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1282 lines
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1282 lines
43 KiB
<!--{
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"Title": "Go 1.7 Release Notes",
|
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"Path": "/doc/go1.7",
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"Template": true
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}-->
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-->
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<!--
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NOTE: In this document and others in this directory, the convention is to
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set fixed-width phrases with non-fixed-width spaces, as in
|
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<code>hello</code> <code>world</code>.
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Do not send CLs removing the interior tags from such phrases.
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-->
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<style>
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main ul li { margin: 0.5em 0; }
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</style>
|
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|
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<h2 id="introduction">Introduction to Go 1.7</h2>
|
|
|
|
<p>
|
|
The latest Go release, version 1.7, arrives six months after 1.6.
|
|
Most of its changes are in the implementation of the toolchain, runtime, and libraries.
|
|
There is one minor change to the language specification.
|
|
As always, the release maintains the Go 1 <a href="/doc/go1compat.html">promise of compatibility</a>.
|
|
We expect almost all Go programs to continue to compile and run as before.
|
|
</p>
|
|
|
|
<p>
|
|
The release <a href="#ports">adds a port to IBM LinuxOne</a>;
|
|
<a href="#compiler">updates the x86-64 compiler back end</a> to generate more efficient code;
|
|
includes the <a href="#context">context package</a>, promoted from the
|
|
<a href="https://golang.org/x/net/context">x/net subrepository</a>
|
|
and now used in the standard library;
|
|
and <a href="#testing">adds support in the testing package</a> for
|
|
creating hierarchies of tests and benchmarks.
|
|
The release also <a href="#cmd_go">finalizes the vendoring support</a>
|
|
started in Go 1.5, making it a standard feature.
|
|
</p>
|
|
|
|
<h2 id="language">Changes to the language</h2>
|
|
|
|
<p>
|
|
There is one tiny language change in this release.
|
|
The section on <a href="/ref/spec#Terminating_statements">terminating statements</a>
|
|
clarifies that to determine whether a statement list ends in a terminating statement,
|
|
the “final non-empty statement” is considered the end,
|
|
matching the existing behavior of the gc and gccgo compiler toolchains.
|
|
In earlier releases the definition referred only to the “final statement,”
|
|
leaving the effect of trailing empty statements at the least unclear.
|
|
The <a href="/pkg/go/types/"><code>go/types</code></a>
|
|
package has been updated to match the gc and gccgo compiler toolchains
|
|
in this respect.
|
|
This change has no effect on the correctness of existing programs.
|
|
</p>
|
|
|
|
<h2 id="ports">Ports</h2>
|
|
|
|
<p>
|
|
Go 1.7 adds support for macOS 10.12 Sierra.
|
|
Binaries built with versions of Go before 1.7 will not work
|
|
correctly on Sierra.
|
|
</p>
|
|
|
|
<p>
|
|
Go 1.7 adds an experimental port to <a href="https://en.wikipedia.org/wiki/Linux_on_z_Systems">Linux on z Systems</a> (<code>linux/s390x</code>)
|
|
and the beginning of a port to Plan 9 on ARM (<code>plan9/arm</code>).
|
|
</p>
|
|
|
|
<p>
|
|
The experimental ports to Linux on 64-bit MIPS (<code>linux/mips64</code> and <code>linux/mips64le</code>)
|
|
added in Go 1.6 now have full support for cgo and external linking.
|
|
</p>
|
|
|
|
<p>
|
|
The experimental port to Linux on little-endian 64-bit PowerPC (<code>linux/ppc64le</code>)
|
|
now requires the POWER8 architecture or later.
|
|
Big-endian 64-bit PowerPC (<code>linux/ppc64</code>) only requires the
|
|
POWER5 architecture.
|
|
</p>
|
|
|
|
<p>
|
|
The OpenBSD port now requires OpenBSD 5.6 or later, for access to the <a href="https://man.openbsd.org/getentropy.2"><i>getentropy</i>(2)</a> system call.
|
|
</p>
|
|
|
|
<h3 id="known_issues">Known Issues</h3>
|
|
|
|
<p>
|
|
There are some instabilities on FreeBSD that are known but not understood.
|
|
These can lead to program crashes in rare cases.
|
|
See <a href="https://golang.org/issue/16136">issue 16136</a>,
|
|
<a href="https://golang.org/issue/15658">issue 15658</a>,
|
|
and <a href="https://golang.org/issue/16396">issue 16396</a>.
|
|
Any help in solving these FreeBSD-specific issues would be appreciated.
|
|
</p>
|
|
|
|
<h2 id="tools">Tools</h2>
|
|
|
|
<h3 id="cmd_asm">Assembler</h3>
|
|
|
|
<p>
|
|
For 64-bit ARM systems, the vector register names have been
|
|
corrected to <code>V0</code> through <code>V31</code>;
|
|
previous releases incorrectly referred to them as <code>V32</code> through <code>V63</code>.
|
|
</p>
|
|
|
|
<p>
|
|
For 64-bit x86 systems, the following instructions have been added:
|
|
<code>PCMPESTRI</code>,
|
|
<code>RORXL</code>,
|
|
<code>RORXQ</code>,
|
|
<code>VINSERTI128</code>,
|
|
<code>VPADDD</code>,
|
|
<code>VPADDQ</code>,
|
|
<code>VPALIGNR</code>,
|
|
<code>VPBLENDD</code>,
|
|
<code>VPERM2F128</code>,
|
|
<code>VPERM2I128</code>,
|
|
<code>VPOR</code>,
|
|
<code>VPSHUFB</code>,
|
|
<code>VPSHUFD</code>,
|
|
<code>VPSLLD</code>,
|
|
<code>VPSLLDQ</code>,
|
|
<code>VPSLLQ</code>,
|
|
<code>VPSRLD</code>,
|
|
<code>VPSRLDQ</code>,
|
|
and
|
|
<code>VPSRLQ</code>.
|
|
</p>
|
|
|
|
<h3 id="compiler">Compiler Toolchain</h3>
|
|
|
|
<p>
|
|
This release includes a new code generation back end for 64-bit x86 systems,
|
|
following a <a href="https://golang.org/s/go17ssa">proposal from 2015</a>
|
|
that has been under development since then.
|
|
The new back end, based on
|
|
<a href="https://en.wikipedia.org/wiki/Static_single_assignment_form">SSA</a>,
|
|
generates more compact, more efficient code
|
|
and provides a better platform for optimizations
|
|
such as bounds check elimination.
|
|
The new back end reduces the CPU time required by
|
|
<a href="https://golang.org/test/bench/go1/">our benchmark programs</a> by 5-35%.
|
|
</p>
|
|
|
|
<p>
|
|
For this release, the new back end can be disabled by passing
|
|
<code>-ssa=0</code> to the compiler.
|
|
If you find that your program compiles or runs successfully
|
|
only with the new back end disabled, please
|
|
<a href="https://golang.org/issue/new">file a bug report</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The format of exported metadata written by the compiler in package archives has changed:
|
|
the old textual format has been replaced by a more compact binary format.
|
|
This results in somewhat smaller package archives and fixes a few
|
|
long-standing corner case bugs.
|
|
</p>
|
|
|
|
<p>
|
|
For this release, the new export format can be disabled by passing
|
|
<code>-newexport=0</code> to the compiler.
|
|
If you find that your program compiles or runs successfully
|
|
only with the new export format disabled, please
|
|
<a href="https://golang.org/issue/new">file a bug report</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The linker's <code>-X</code> option no longer supports the unusual two-argument form
|
|
<code>-X</code> <code>name</code> <code>value</code>,
|
|
as <a href="/doc/go1.6#compiler">announced</a> in the Go 1.6 release
|
|
and in warnings printed by the linker.
|
|
Use <code>-X</code> <code>name=value</code> instead.
|
|
</p>
|
|
|
|
<p>
|
|
The compiler and linker have been optimized and run significantly faster in this release than in Go 1.6,
|
|
although they are still slower than we would like and will continue to be optimized in future releases.
|
|
</p>
|
|
|
|
<p>
|
|
Due to changes across the compiler toolchain and standard library,
|
|
binaries built with this release should typically be smaller than binaries
|
|
built with Go 1.6,
|
|
sometimes by as much as 20-30%.
|
|
</p>
|
|
|
|
<p>
|
|
On x86-64 systems, Go programs now maintain stack frame pointers
|
|
as expected by profiling tools like Linux's perf and Intel's VTune,
|
|
making it easier to analyze and optimize Go programs using these tools.
|
|
The frame pointer maintenance has a small run-time overhead that varies
|
|
but averages around 2%. We hope to reduce this cost in future releases.
|
|
To build a toolchain that does not use frame pointers, set
|
|
<code>GOEXPERIMENT=noframepointer</code> when running
|
|
<code>make.bash</code>, <code>make.bat</code>, or <code>make.rc</code>.
|
|
</p>
|
|
|
|
<h3 id="cmd_cgo">Cgo</h3>
|
|
|
|
<p>
|
|
Packages using <a href="/cmd/cgo/">cgo</a> may now include
|
|
Fortran source files (in addition to C, C++, Objective C, and SWIG),
|
|
although the Go bindings must still use C language APIs.
|
|
</p>
|
|
|
|
<p>
|
|
Go bindings may now use a new helper function <code>C.CBytes</code>.
|
|
In contrast to <code>C.CString</code>, which takes a Go <code>string</code>
|
|
and returns a <code>*C.byte</code> (a C <code>char*</code>),
|
|
<code>C.CBytes</code> takes a Go <code>[]byte</code>
|
|
and returns an <code>unsafe.Pointer</code> (a C <code>void*</code>).
|
|
</p>
|
|
|
|
<p>
|
|
Packages and binaries built using <code>cgo</code> have in past releases
|
|
produced different output on each build,
|
|
due to the embedding of temporary directory names.
|
|
When using this release with
|
|
new enough versions of GCC or Clang
|
|
(those that support the <code>-fdebug-prefix-map</code> option),
|
|
those builds should finally be deterministic.
|
|
</p>
|
|
|
|
<h3 id="gccgo">Gccgo</h3>
|
|
|
|
<p>
|
|
Due to the alignment of Go's semiannual release schedule with GCC's annual release schedule,
|
|
GCC release 6 contains the Go 1.6.1 version of gccgo.
|
|
The next release, GCC 7, will likely have the Go 1.8 version of gccgo.
|
|
</p>
|
|
|
|
<h3 id="cmd_go">Go command</h3>
|
|
|
|
<p>
|
|
The <a href="/cmd/go/"><code>go</code></a> command's basic operation
|
|
is unchanged, but there are a number of changes worth noting.
|
|
</p>
|
|
|
|
<p>
|
|
This release removes support for the <code>GO15VENDOREXPERIMENT</code> environment variable,
|
|
as <a href="/doc/go1.6#go_command">announced</a> in the Go 1.6 release.
|
|
<a href="https://golang.org/s/go15vendor">Vendoring support</a>
|
|
is now a standard feature of the <code>go</code> command and toolchain.
|
|
</p>
|
|
|
|
<p>
|
|
The <code>Package</code> data structure made available to
|
|
“<code>go</code> <code>list</code>” now includes a
|
|
<code>StaleReason</code> field explaining why a particular package
|
|
is or is not considered stale (in need of rebuilding).
|
|
This field is available to the <code>-f</code> or <code>-json</code>
|
|
options and is useful for understanding why a target is being rebuilt.
|
|
</p>
|
|
|
|
<p>
|
|
The “<code>go</code> <code>get</code>” command now supports
|
|
import paths referring to <code>git.openstack.org</code>.
|
|
</p>
|
|
|
|
<p>
|
|
This release adds experimental, minimal support for building programs using
|
|
<a href="/pkg/go/build#hdr-Binary_Only_Packages">binary-only packages</a>,
|
|
packages distributed in binary form
|
|
without the corresponding source code.
|
|
This feature is needed in some commercial settings
|
|
but is not intended to be fully integrated into the rest of the toolchain.
|
|
For example, tools that assume access to complete source code
|
|
will not work with such packages, and there are no plans to support
|
|
such packages in the “<code>go</code> <code>get</code>” command.
|
|
</p>
|
|
|
|
<h3 id="cmd_doc">Go doc</h3>
|
|
|
|
<p>
|
|
The “<code>go</code> <code>doc</code>” command
|
|
now groups constructors with the type they construct,
|
|
following <a href="/cmd/godoc/"><code>godoc</code></a>.
|
|
</p>
|
|
|
|
<h3 id="cmd_vet">Go vet</h3>
|
|
|
|
<p>
|
|
The “<code>go</code> <code>vet</code>” command
|
|
has more accurate analysis in its <code>-copylock</code> and <code>-printf</code> checks,
|
|
and a new <code>-tests</code> check that checks the name and signature of likely test functions.
|
|
To avoid confusion with the new <code>-tests</code> check, the old, unadvertised
|
|
<code>-test</code> option has been removed; it was equivalent to <code>-all</code> <code>-shadow</code>.
|
|
</p>
|
|
|
|
<p id="vet_lostcancel">
|
|
The <code>vet</code> command also has a new check,
|
|
<code>-lostcancel</code>, which detects failure to call the
|
|
cancelation function returned by the <code>WithCancel</code>,
|
|
<code>WithTimeout</code>, and <code>WithDeadline</code> functions in
|
|
Go 1.7's new <code>context</code> package (see <a
|
|
href='#context'>below</a>).
|
|
Failure to call the function prevents the new <code>Context</code>
|
|
from being reclaimed until its parent is cancelled.
|
|
(The background context is never cancelled.)
|
|
</p>
|
|
|
|
<h3 id="cmd_dist">Go tool dist</h3>
|
|
|
|
<p>
|
|
The new subcommand “<code>go</code> <code>tool</code> <code>dist</code> <code>list</code>”
|
|
prints all supported operating system/architecture pairs.
|
|
</p>
|
|
|
|
<h3 id="cmd_trace">Go tool trace</h3>
|
|
|
|
<p>
|
|
The “<code>go</code> <code>tool</code> <code>trace</code>” command,
|
|
<a href="/doc/go1.5#trace_command">introduced in Go 1.5</a>,
|
|
has been refined in various ways.
|
|
</p>
|
|
|
|
<p>
|
|
First, collecting traces is significantly more efficient than in past releases.
|
|
In this release, the typical execution-time overhead of collecting a trace is about 25%;
|
|
in past releases it was at least 400%.
|
|
Second, trace files now include file and line number information,
|
|
making them more self-contained and making the
|
|
original executable optional when running the trace tool.
|
|
Third, the trace tool now breaks up large traces to avoid limits
|
|
in the browser-based viewer.
|
|
</p>
|
|
|
|
<p>
|
|
Although the trace file format has changed in this release,
|
|
the Go 1.7 tools can still read traces from earlier releases.
|
|
</p>
|
|
|
|
<h2 id="performance">Performance</h2>
|
|
|
|
<p>
|
|
As always, the changes are so general and varied that precise statements
|
|
about performance are difficult to make.
|
|
Most programs should run a bit faster,
|
|
due to speedups in the garbage collector and
|
|
optimizations in the core library.
|
|
On x86-64 systems, many programs will run significantly faster,
|
|
due to improvements in generated code brought by the
|
|
new compiler back end.
|
|
As noted above, in our own benchmarks,
|
|
the code generation changes alone typically reduce program CPU time by 5-35%.
|
|
</p>
|
|
|
|
<p>
|
|
<!-- git log -''-grep '-[0-9][0-9]\.[0-9][0-9]%' go1.6.. -->
|
|
There have been significant optimizations bringing more than 10% improvements
|
|
to implementations in the
|
|
<a href="/pkg/crypto/sha1/"><code>crypto/sha1</code></a>,
|
|
<a href="/pkg/crypto/sha256/"><code>crypto/sha256</code></a>,
|
|
<a href="/pkg/encoding/binary/"><code>encoding/binary</code></a>,
|
|
<a href="/pkg/fmt/"><code>fmt</code></a>,
|
|
<a href="/pkg/hash/adler32/"><code>hash/adler32</code></a>,
|
|
<a href="/pkg/hash/crc32/"><code>hash/crc32</code></a>,
|
|
<a href="/pkg/hash/crc64/"><code>hash/crc64</code></a>,
|
|
<a href="/pkg/image/color/"><code>image/color</code></a>,
|
|
<a href="/pkg/math/big/"><code>math/big</code></a>,
|
|
<a href="/pkg/strconv/"><code>strconv</code></a>,
|
|
<a href="/pkg/strings/"><code>strings</code></a>,
|
|
<a href="/pkg/unicode/"><code>unicode</code></a>,
|
|
and
|
|
<a href="/pkg/unicode/utf16/"><code>unicode/utf16</code></a>
|
|
packages.
|
|
</p>
|
|
|
|
<p>
|
|
Garbage collection pauses should be significantly shorter than they
|
|
were in Go 1.6 for programs with large numbers of idle goroutines,
|
|
substantial stack size fluctuation, or large package-level variables.
|
|
</p>
|
|
|
|
<h2 id="library">Core library</h2>
|
|
|
|
<h3 id="context">Context</h3>
|
|
|
|
<p>
|
|
Go 1.7 moves the <code>golang.org/x/net/context</code> package
|
|
into the standard library as <a href="/pkg/context/"><code>context</code></a>.
|
|
This allows the use of contexts for cancelation, timeouts, and passing
|
|
request-scoped data in other standard library packages,
|
|
including
|
|
<a href="#net">net</a>,
|
|
<a href="#net_http">net/http</a>,
|
|
and
|
|
<a href="#os_exec">os/exec</a>,
|
|
as noted below.
|
|
</p>
|
|
|
|
<p>
|
|
For more information about contexts, see the
|
|
<a href="/pkg/context/">package documentation</a>
|
|
and the Go blog post
|
|
“<a href="https://blog.golang.org/context">Go Concurrent Patterns: Context</a>.”
|
|
</p>
|
|
|
|
<h3 id="httptrace">HTTP Tracing</h3>
|
|
|
|
<p>
|
|
Go 1.7 introduces <a href="/pkg/net/http/httptrace/"><code>net/http/httptrace</code></a>,
|
|
a package that provides mechanisms for tracing events within HTTP requests.
|
|
</p>
|
|
|
|
<h3 id="testing">Testing</h3>
|
|
|
|
<p>
|
|
The <code>testing</code> package now supports the definition
|
|
of tests with subtests and benchmarks with sub-benchmarks.
|
|
This support makes it easy to write table-driven benchmarks
|
|
and to create hierarchical tests.
|
|
It also provides a way to share common setup and tear-down code.
|
|
See the <a href="/pkg/testing/#hdr-Subtests_and_Sub_benchmarks">package documentation</a> for details.
|
|
</p>
|
|
|
|
<h3 id="runtime">Runtime</h3>
|
|
|
|
<p>
|
|
All panics started by the runtime now use panic values
|
|
that implement both the
|
|
builtin <a href="/ref/spec#Errors"><code>error</code></a>,
|
|
and
|
|
<a href="/pkg/runtime/#Error"><code>runtime.Error</code></a>,
|
|
as
|
|
<a href="/ref/spec#Run_time_panics">required by the language specification</a>.
|
|
</p>
|
|
|
|
<p>
|
|
During panics, if a signal's name is known, it will be printed in the stack trace.
|
|
Otherwise, the signal's number will be used, as it was before Go1.7.
|
|
</p>
|
|
|
|
<p>
|
|
The new function
|
|
<a href="/pkg/runtime/#KeepAlive"><code>KeepAlive</code></a>
|
|
provides an explicit mechanism for declaring
|
|
that an allocated object must be considered reachable
|
|
at a particular point in a program,
|
|
typically to delay the execution of an associated finalizer.
|
|
</p>
|
|
|
|
<p>
|
|
The new function
|
|
<a href="/pkg/runtime/#CallersFrames"><code>CallersFrames</code></a>
|
|
translates a PC slice obtained from
|
|
<a href="/pkg/runtime/#Callers"><code>Callers</code></a>
|
|
into a sequence of frames corresponding to the call stack.
|
|
This new API should be preferred instead of direct use of
|
|
<a href="/pkg/runtime/#FuncForPC"><code>FuncForPC</code></a>,
|
|
because the frame sequence can more accurately describe
|
|
call stacks with inlined function calls.
|
|
</p>
|
|
|
|
<p>
|
|
The new function
|
|
<a href="/pkg/runtime/#SetCgoTraceback"><code>SetCgoTraceback</code></a>
|
|
facilitates tighter integration between Go and C code executing
|
|
in the same process called using cgo.
|
|
</p>
|
|
|
|
<p>
|
|
On 32-bit systems, the runtime can now use memory allocated
|
|
by the operating system anywhere in the address space,
|
|
eliminating the
|
|
“memory allocated by OS not in usable range” failure
|
|
common in some environments.
|
|
</p>
|
|
|
|
<p>
|
|
The runtime can now return unused memory to the operating system on
|
|
all architectures.
|
|
In Go 1.6 and earlier, the runtime could not
|
|
release memory on ARM64, 64-bit PowerPC, or MIPS.
|
|
</p>
|
|
|
|
<p>
|
|
On Windows, Go programs in Go 1.5 and earlier forced
|
|
the global Windows timer resolution to 1ms at startup
|
|
by calling <code>timeBeginPeriod(1)</code>.
|
|
Changing the global timer resolution caused problems on some systems,
|
|
and testing suggested that the call was not needed for good scheduler performance,
|
|
so Go 1.6 removed the call.
|
|
Go 1.7 brings the call back: under some workloads the call
|
|
is still needed for good scheduler performance.
|
|
</p>
|
|
|
|
|
|
<h3 id="minor_library_changes">Minor changes to the library</h3>
|
|
|
|
<p>
|
|
As always, there are various minor changes and updates to the library,
|
|
made with the Go 1 <a href="/doc/go1compat">promise of compatibility</a>
|
|
in mind.
|
|
</p>
|
|
|
|
<dl id="bufio"><dt><a href="/pkg/bufio/">bufio</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
In previous releases of Go, if
|
|
<a href="/pkg/bufio/#Reader"><code>Reader</code></a>'s
|
|
<a href="/pkg/bufio/#Reader.Peek"><code>Peek</code></a> method
|
|
were asked for more bytes than fit in the underlying buffer,
|
|
it would return an empty slice and the error <code>ErrBufferFull</code>.
|
|
Now it returns the entire underlying buffer, still accompanied by the error <code>ErrBufferFull</code>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="bytes"><dt><a href="/pkg/bytes/">bytes</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The new functions
|
|
<a href="/pkg/bytes/#ContainsAny"><code>ContainsAny</code></a> and
|
|
<a href="/pkg/bytes/#ContainsRune"><code>ContainsRune</code></a>
|
|
have been added for symmetry with
|
|
the <a href="/pkg/strings/"><code>strings</code></a> package.
|
|
</p>
|
|
|
|
<p>
|
|
In previous releases of Go, if
|
|
<a href="/pkg/bytes/#Reader"><code>Reader</code></a>'s
|
|
<a href="/pkg/bytes/#Reader.Read"><code>Read</code></a> method
|
|
were asked for zero bytes with no data remaining, it would
|
|
return a count of 0 and no error.
|
|
Now it returns a count of 0 and the error
|
|
<a href="/pkg/io/#EOF"><code>io.EOF</code></a>.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/bytes/#Reader"><code>Reader</code></a> type has a new method
|
|
<a href="/pkg/bytes/#Reader.Reset"><code>Reset</code></a> to allow reuse of a <code>Reader</code>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="compress_flate"><dt><a href="/pkg/compress/flate/">compress/flate</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
There are many performance optimizations throughout the package.
|
|
Decompression speed is improved by about 10%,
|
|
while compression for <code>DefaultCompression</code> is twice as fast.
|
|
</p>
|
|
|
|
<p>
|
|
In addition to those general improvements,
|
|
the
|
|
<code>BestSpeed</code>
|
|
compressor has been replaced entirely and uses an
|
|
algorithm similar to <a href="https://github.com/google/snappy">Snappy</a>,
|
|
resulting in about a 2.5X speed increase,
|
|
although the output can be 5-10% larger than with the previous algorithm.
|
|
</p>
|
|
|
|
<p>
|
|
There is also a new compression level
|
|
<code>HuffmanOnly</code>
|
|
that applies Huffman but not Lempel-Ziv encoding.
|
|
<a href="https://blog.klauspost.com/constant-time-gzipzip-compression/">Forgoing Lempel-Ziv encoding</a> means that
|
|
<code>HuffmanOnly</code> runs about 3X faster than the new <code>BestSpeed</code>
|
|
but at the cost of producing compressed outputs that are 20-40% larger than those
|
|
generated by the new <code>BestSpeed</code>.
|
|
</p>
|
|
|
|
<p>
|
|
It is important to note that both
|
|
<code>BestSpeed</code> and <code>HuffmanOnly</code> produce a compressed output that is
|
|
<a href="https://tools.ietf.org/html/rfc1951">RFC 1951</a> compliant.
|
|
In other words, any valid DEFLATE decompressor will continue to be able to decompress these outputs.
|
|
</p>
|
|
|
|
<p>
|
|
Lastly, there is a minor change to the decompressor's implementation of
|
|
<a href="/pkg/io/#Reader"><code>io.Reader</code></a>. In previous versions,
|
|
the decompressor deferred reporting
|
|
<a href="/pkg/io/#EOF"><code>io.EOF</code></a> until exactly no more bytes could be read.
|
|
Now, it reports
|
|
<a href="/pkg/io/#EOF"><code>io.EOF</code></a> more eagerly when reading the last set of bytes.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="crypto_tls"><dt><a href="/pkg/crypto/tls/">crypto/tls</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The TLS implementation sends the first few data packets on each connection
|
|
using small record sizes, gradually increasing to the TLS maximum record size.
|
|
This heuristic reduces the amount of data that must be received before
|
|
the first packet can be decrypted, improving communication latency over
|
|
low-bandwidth networks.
|
|
Setting
|
|
<a href="/pkg/crypto/tls/#Config"><code>Config</code></a>'s
|
|
<code>DynamicRecordSizingDisabled</code> field to true
|
|
forces the behavior of Go 1.6 and earlier, where packets are
|
|
as large as possible from the start of the connection.
|
|
</p>
|
|
|
|
<p>
|
|
The TLS client now has optional, limited support for server-initiated renegotiation,
|
|
enabled by setting the
|
|
<a href="/pkg/crypto/tls/#Config"><code>Config</code></a>'s
|
|
<code>Renegotiation</code> field.
|
|
This is needed for connecting to many Microsoft Azure servers.
|
|
</p>
|
|
|
|
<p>
|
|
The errors returned by the package now consistently begin with a
|
|
<code>tls:</code> prefix.
|
|
In past releases, some errors used a <code>crypto/tls:</code> prefix,
|
|
some used a <code>tls:</code> prefix, and some had no prefix at all.
|
|
</p>
|
|
|
|
<p>
|
|
When generating self-signed certificates, the package no longer sets the
|
|
“Authority Key Identifier” field by default.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="crypto_x509"><dt><a href="/pkg/crypto/x509/">crypto/x509</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The new function
|
|
<a href="/pkg/crypto/x509/#SystemCertPool"><code>SystemCertPool</code></a>
|
|
provides access to the entire system certificate pool if available.
|
|
There is also a new associated error type
|
|
<a href="/pkg/crypto/x509/#SystemRootsError"><code>SystemRootsError</code></a>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="debug_dwarf"><dt><a href="/pkg/debug/dwarf/">debug/dwarf</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/debug/dwarf/#Reader"><code>Reader</code></a> type's new
|
|
<a href="/pkg/debug/dwarf/#Reader.SeekPC"><code>SeekPC</code></a> method and the
|
|
<a href="/pkg/debug/dwarf/#Data"><code>Data</code></a> type's new
|
|
<a href="/pkg/debug/dwarf/#Ranges"><code>Ranges</code></a> method
|
|
help to find the compilation unit to pass to a
|
|
<a href="/pkg/debug/dwarf/#LineReader"><code>LineReader</code></a>
|
|
and to identify the specific function for a given program counter.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="debug_elf"><dt><a href="/pkg/debug/elf/">debug/elf</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The new
|
|
<a href="/pkg/debug/elf/#R_390"><code>R_390</code></a> relocation type
|
|
and its many predefined constants
|
|
support the S390 port.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="encoding_asn1"><dt><a href="/pkg/encoding/asn1/">encoding/asn1</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The ASN.1 decoder now rejects non-minimal integer encodings.
|
|
This may cause the package to reject some invalid but formerly accepted ASN.1 data.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="encoding_json"><dt><a href="/pkg/encoding/json/">encoding/json</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/encoding/json/#Encoder"><code>Encoder</code></a>'s new
|
|
<a href="/pkg/encoding/json/#Encoder.SetIndent"><code>SetIndent</code></a> method
|
|
sets the indentation parameters for JSON encoding,
|
|
like in the top-level
|
|
<a href="/pkg/encoding/json/#Indent"><code>Indent</code></a> function.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/encoding/json/#Encoder"><code>Encoder</code></a>'s new
|
|
<a href="/pkg/encoding/json/#Encoder.SetEscapeHTML"><code>SetEscapeHTML</code></a> method
|
|
controls whether the
|
|
<code>&</code>, <code><</code>, and <code>></code>
|
|
characters in quoted strings should be escaped as
|
|
<code>\u0026</code>, <code>\u003c</code>, and <code>\u003e</code>,
|
|
respectively.
|
|
As in previous releases, the encoder defaults to applying this escaping,
|
|
to avoid certain problems that can arise when embedding JSON in HTML.
|
|
</p>
|
|
|
|
<p>
|
|
In earlier versions of Go, this package only supported encoding and decoding
|
|
maps using keys with string types.
|
|
Go 1.7 adds support for maps using keys with integer types:
|
|
the encoding uses a quoted decimal representation as the JSON key.
|
|
Go 1.7 also adds support for encoding maps using non-string keys that implement
|
|
the <code>MarshalText</code>
|
|
(see
|
|
<a href="/pkg/encoding/#TextMarshaler"><code>encoding.TextMarshaler</code></a>)
|
|
method,
|
|
as well as support for decoding maps using non-string keys that implement
|
|
the <code>UnmarshalText</code>
|
|
(see
|
|
<a href="/pkg/encoding/#TextUnmarshaler"><code>encoding.TextUnmarshaler</code></a>)
|
|
method.
|
|
These methods are ignored for keys with string types in order to preserve
|
|
the encoding and decoding used in earlier versions of Go.
|
|
</p>
|
|
|
|
<p>
|
|
When encoding a slice of typed bytes,
|
|
<a href="/pkg/encoding/json/#Marshal"><code>Marshal</code></a>
|
|
now generates an array of elements encoded using
|
|
that byte type's
|
|
<code>MarshalJSON</code>
|
|
or
|
|
<code>MarshalText</code>
|
|
method if present,
|
|
only falling back to the default base64-encoded string data if neither method is available.
|
|
Earlier versions of Go accept both the original base64-encoded string encoding
|
|
and the array encoding (assuming the byte type also implements
|
|
<code>UnmarshalJSON</code>
|
|
or
|
|
<code>UnmarshalText</code>
|
|
as appropriate),
|
|
so this change should be semantically backwards compatible with earlier versions of Go,
|
|
even though it does change the chosen encoding.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="go_build"><dt><a href="/pkg/go/build/">go/build</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
To implement the go command's new support for binary-only packages
|
|
and for Fortran code in cgo-based packages,
|
|
the
|
|
<a href="/pkg/go/build/#Package"><code>Package</code></a> type
|
|
adds new fields <code>BinaryOnly</code>, <code>CgoFFLAGS</code>, and <code>FFiles</code>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="go_doc"><dt><a href="/pkg/go/doc/">go/doc</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
To support the corresponding change in <code>go</code> <code>test</code> described above,
|
|
<a href="/pkg/go/doc/#Example"><code>Example</code></a> struct adds a Unordered field
|
|
indicating whether the example may generate its output lines in any order.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="io"><dt><a href="/pkg/io/">io</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The package adds new constants
|
|
<code>SeekStart</code>, <code>SeekCurrent</code>, and <code>SeekEnd</code>,
|
|
for use with
|
|
<a href="/pkg/io/#Seeker"><code>Seeker</code></a>
|
|
implementations.
|
|
These constants are preferred over <code>os.SEEK_SET</code>, <code>os.SEEK_CUR</code>, and <code>os.SEEK_END</code>,
|
|
but the latter will be preserved for compatibility.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="math_big"><dt><a href="/pkg/math/big/">math/big</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/math/big/#Float"><code>Float</code></a> type adds
|
|
<a href="/pkg/math/big/#Float.GobEncode"><code>GobEncode</code></a> and
|
|
<a href="/pkg/math/big/#Float.GobDecode"><code>GobDecode</code></a> methods,
|
|
so that values of type <code>Float</code> can now be encoded and decoded using the
|
|
<a href="/pkg/encoding/gob/"><code>encoding/gob</code></a>
|
|
package.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="math_rand"><dt><a href="/pkg/math/rand/">math/rand</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/math/rand/#Read"><code>Read</code></a> function and
|
|
<a href="/pkg/math/rand/#Rand"><code>Rand</code></a>'s
|
|
<a href="/pkg/math/rand/#Rand.Read"><code>Read</code></a> method
|
|
now produce a pseudo-random stream of bytes that is consistent and not
|
|
dependent on the size of the input buffer.
|
|
</p>
|
|
|
|
<p>
|
|
The documentation clarifies that
|
|
Rand's <a href="/pkg/math/rand/#Rand.Seed"><code>Seed</code></a>
|
|
and <a href="/pkg/math/rand/#Rand.Read"><code>Read</code></a> methods
|
|
are not safe to call concurrently, though the global
|
|
functions <a href="/pkg/math/rand/#Seed"><code>Seed</code></a>
|
|
and <a href="/pkg/math/rand/#Read"><code>Read</code></a> are (and have
|
|
always been) safe.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="mime_multipart"><dt><a href="/pkg/mime/multipart/">mime/multipart</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/mime/multipart/#Writer"><code>Writer</code></a>
|
|
implementation now emits each multipart section's header sorted by key.
|
|
Previously, iteration over a map caused the section header to use a
|
|
non-deterministic order.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net"><dt><a href="/pkg/net/">net</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
As part of the introduction of <a href="#context">context</a>, the
|
|
<a href="/pkg/net/#Dialer"><code>Dialer</code></a> type has a new method
|
|
<a href="/pkg/net/#Dialer.DialContext"><code>DialContext</code></a>, like
|
|
<a href="/pkg/net/#Dialer.Dial"><code>Dial</code></a> but adding the
|
|
<a href="/pkg/context/#Context"><code>context.Context</code></a>
|
|
for the dial operation.
|
|
The context is intended to obsolete the <code>Dialer</code>'s
|
|
<code>Cancel</code> and <code>Deadline</code> fields,
|
|
but the implementation continues to respect them,
|
|
for backwards compatibility.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/#IP"><code>IP</code></a> type's
|
|
<a href="/pkg/net/#IP.String"><code>String</code></a> method has changed its result for invalid <code>IP</code> addresses.
|
|
In past releases, if an <code>IP</code> byte slice had length other than 0, 4, or 16, <code>String</code>
|
|
returned <code>"?"</code>.
|
|
Go 1.7 adds the hexadecimal encoding of the bytes, as in <code>"?12ab"</code>.
|
|
</p>
|
|
|
|
<p>
|
|
The pure Go <a href="/pkg/net/#hdr-Name_Resolution">name resolution</a>
|
|
implementation now respects <code>nsswitch.conf</code>'s
|
|
stated preference for the priority of DNS lookups compared to
|
|
local file (that is, <code>/etc/hosts</code>) lookups.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_http"><dt><a href="/pkg/net/http/">net/http</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
<a href="/pkg/net/http/#ResponseWriter"><code>ResponseWriter</code></a>'s
|
|
documentation now makes clear that beginning to write the response
|
|
may prevent future reads on the request body.
|
|
For maximal compatibility, implementations are encouraged to
|
|
read the request body completely before writing any part of the response.
|
|
</p>
|
|
|
|
<p>
|
|
As part of the introduction of <a href="#context">context</a>, the
|
|
<a href="/pkg/net/http/#Request"><code>Request</code></a> has a new methods
|
|
<a href="/pkg/net/http/#Request.Context"><code>Context</code></a>, to retrieve the associated context, and
|
|
<a href="/pkg/net/http/#Request.WithContext"><code>WithContext</code></a>, to construct a copy of <code>Request</code>
|
|
with a modified context.
|
|
</p>
|
|
|
|
<p>
|
|
In the
|
|
<a href="/pkg/net/http/#Server"><code>Server</code></a> implementation,
|
|
<a href="/pkg/net/http/#Server.Serve"><code>Serve</code></a> records in the request context
|
|
both the underlying <code>*Server</code> using the key <code>ServerContextKey</code>
|
|
and the local address on which the request was received (a
|
|
<a href="/pkg/net/#Addr"><code>Addr</code></a>) using the key <code>LocalAddrContextKey</code>.
|
|
For example, the address on which a request received is
|
|
<code>req.Context().Value(http.LocalAddrContextKey).(net.Addr)</code>.
|
|
</p>
|
|
|
|
<p>
|
|
The server's <a href="/pkg/net/http/#Server.Serve"><code>Serve</code></a> method
|
|
now only enables HTTP/2 support if the <code>Server.TLSConfig</code> field is <code>nil</code>
|
|
or includes <code>"h2"</code> in its <code>TLSConfig.NextProtos</code>.
|
|
</p>
|
|
|
|
<p>
|
|
The server implementation now
|
|
pads response codes less than 100 to three digits
|
|
as required by the protocol,
|
|
so that <code>w.WriteHeader(5)</code> uses the HTTP response
|
|
status <code>005</code>, not just <code>5</code>.
|
|
</p>
|
|
|
|
<p>
|
|
The server implementation now correctly sends only one "Transfer-Encoding" header when "chunked"
|
|
is set explicitly, following <a href="https://tools.ietf.org/html/rfc7230#section-3.3.1">RFC 7230</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The server implementation is now stricter about rejecting requests with invalid HTTP versions.
|
|
Invalid requests claiming to be HTTP/0.x are now rejected (HTTP/0.9 was never fully supported),
|
|
and plaintext HTTP/2 requests other than the "PRI * HTTP/2.0" upgrade request are now rejected as well.
|
|
The server continues to handle encrypted HTTP/2 requests.
|
|
</p>
|
|
|
|
<p>
|
|
In the server, a 200 status code is sent back by the timeout handler on an empty
|
|
response body, instead of sending back 0 as the status code.
|
|
</p>
|
|
|
|
<p>
|
|
In the client, the
|
|
<a href="/pkg/net/http/#Transport"><code>Transport</code></a> implementation passes the request context
|
|
to any dial operation connecting to the remote server.
|
|
If a custom dialer is needed, the new <code>Transport</code> field
|
|
<code>DialContext</code> is preferred over the existing <code>Dial</code> field,
|
|
to allow the transport to supply a context.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/http/#Transport"><code>Transport</code></a> also adds fields
|
|
<code>IdleConnTimeout</code>,
|
|
<code>MaxIdleConns</code>,
|
|
and
|
|
<code>MaxResponseHeaderBytes</code>
|
|
to help control client resources consumed
|
|
by idle or chatty servers.
|
|
</p>
|
|
|
|
<p>
|
|
A
|
|
<a href="/pkg/net/http/#Client"><code>Client</code></a>'s configured <code>CheckRedirect</code> function can now
|
|
return <code>ErrUseLastResponse</code> to indicate that the
|
|
most recent redirect response should be returned as the
|
|
result of the HTTP request.
|
|
That response is now available to the <code>CheckRedirect</code> function
|
|
as <code>req.Response</code>.
|
|
</p>
|
|
|
|
<p>
|
|
Since Go 1, the default behavior of the HTTP client is
|
|
to request server-side compression
|
|
using the <code>Accept-Encoding</code> request header
|
|
and then to decompress the response body transparently,
|
|
and this behavior is adjustable using the
|
|
<a href="/pkg/net/http/#Transport"><code>Transport</code></a>'s <code>DisableCompression</code> field.
|
|
In Go 1.7, to aid the implementation of HTTP proxies, the
|
|
<a href="/pkg/net/http/#Response"><code>Response</code></a>'s new
|
|
<code>Uncompressed</code> field reports whether
|
|
this transparent decompression took place.
|
|
</p>
|
|
|
|
<p>
|
|
<a href="/pkg/net/http/#DetectContentType"><code>DetectContentType</code></a>
|
|
adds support for a few new audio and video content types.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_http_cgi"><dt><a href="/pkg/net/http/cgi/">net/http/cgi</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/http/cgi/#Handler"><code>Handler</code></a>
|
|
adds a new field
|
|
<code>Stderr</code>
|
|
that allows redirection of the child process's
|
|
standard error away from the host process's
|
|
standard error.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_http_httptest"><dt><a href="/pkg/net/http/httptest/">net/http/httptest</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The new function
|
|
<a href="/pkg/net/http/httptest/#NewRequest"><code>NewRequest</code></a>
|
|
prepares a new
|
|
<a href="/pkg/net/http/#Request"><code>http.Request</code></a>
|
|
suitable for passing to an
|
|
<a href="/pkg/net/http/#Handler"><code>http.Handler</code></a> during a test.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/http/httptest/#ResponseRecorder"><code>ResponseRecorder</code></a>'s new
|
|
<a href="/pkg/net/http/httptest/#ResponseRecorder.Result"><code>Result</code></a> method
|
|
returns the recorded
|
|
<a href="/pkg/net/http/#Response"><code>http.Response</code></a>.
|
|
Tests that need to check the response's headers or trailers
|
|
should call <code>Result</code> and inspect the response fields
|
|
instead of accessing
|
|
<code>ResponseRecorder</code>'s <code>HeaderMap</code> directly.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_http_httputil"><dt><a href="/pkg/net/http/httputil/">net/http/httputil</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/http/httputil/#ReverseProxy"><code>ReverseProxy</code></a> implementation now responds with “502 Bad Gateway”
|
|
when it cannot reach a back end; in earlier releases it responded with “500 Internal Server Error.”
|
|
</p>
|
|
|
|
<p>
|
|
Both
|
|
<a href="/pkg/net/http/httputil/#ClientConn"><code>ClientConn</code></a> and
|
|
<a href="/pkg/net/http/httputil/#ServerConn"><code>ServerConn</code></a> have been documented as deprecated.
|
|
They are low-level, old, and unused by Go's current HTTP stack
|
|
and will no longer be updated.
|
|
Programs should use
|
|
<a href="/pkg/net/http/#Client"><code>http.Client</code></a>,
|
|
<a href="/pkg/net/http/#Transport"><code>http.Transport</code></a>,
|
|
and
|
|
<a href="/pkg/net/http/#Server"><code>http.Server</code></a>
|
|
instead.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_http_pprof"><dt><a href="/pkg/net/http/pprof/">net/http/pprof</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The runtime trace HTTP handler, installed to handle the path <code>/debug/pprof/trace</code>,
|
|
now accepts a fractional number in its <code>seconds</code> query parameter,
|
|
allowing collection of traces for intervals smaller than one second.
|
|
This is especially useful on busy servers.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl><dt><a href="/pkg/net/mail/">net/mail</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The address parser now allows unescaped UTF-8 text in addresses
|
|
following <a href="https://tools.ietf.org/html/rfc6532">RFC 6532</a>,
|
|
but it does not apply any normalization to the result.
|
|
For compatibility with older mail parsers,
|
|
the address encoder, namely
|
|
<a href="/pkg/net/mail/#Address"><code>Address</code></a>'s
|
|
<a href="/pkg/net/mail/#Address.String"><code>String</code></a> method,
|
|
continues to escape all UTF-8 text following <a href="https://tools.ietf.org/html/rfc5322">RFC 5322</a>.
|
|
</p>
|
|
|
|
<p>
|
|
The <a href="/pkg/net/mail/#ParseAddress"><code>ParseAddress</code></a>
|
|
function and
|
|
the <a href="/pkg/net/mail/#AddressParser.Parse"><code>AddressParser.Parse</code></a>
|
|
method are stricter.
|
|
They used to ignore any characters following an e-mail address, but
|
|
will now return an error for anything other than whitespace.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="net_url"><dt><a href="/pkg/net/url/">net/url</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/net/url/#URL"><code>URL</code></a>'s
|
|
new <code>ForceQuery</code> field
|
|
records whether the URL must have a query string,
|
|
in order to distinguish URLs without query strings (like <code>/search</code>)
|
|
from URLs with empty query strings (like <code>/search?</code>).
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="os"><dt><a href="/pkg/os/">os</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
<a href="/pkg/os/#IsExist"><code>IsExist</code></a> now returns true for <code>syscall.ENOTEMPTY</code>,
|
|
on systems where that error exists.
|
|
</p>
|
|
|
|
<p>
|
|
On Windows,
|
|
<a href="/pkg/os/#Remove"><code>Remove</code></a> now removes read-only files when possible,
|
|
making the implementation behave as on
|
|
non-Windows systems.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="os_exec"><dt><a href="/pkg/os/exec/">os/exec</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
As part of the introduction of <a href="#context">context</a>,
|
|
the new constructor
|
|
<a href="/pkg/os/exec/#CommandContext"><code>CommandContext</code></a>
|
|
is like
|
|
<a href="/pkg/os/exec/#Command"><code>Command</code></a> but includes a context that can be used to cancel the command execution.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="os_user"><dt><a href="/pkg/os/user/">os/user</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The
|
|
<a href="/pkg/os/user/#Current"><code>Current</code></a>
|
|
function is now implemented even when cgo is not available.
|
|
</p>
|
|
|
|
<p>
|
|
The new
|
|
<a href="/pkg/os/user/#Group"><code>Group</code></a> type,
|
|
along with the lookup functions
|
|
<a href="/pkg/os/user/#LookupGroup"><code>LookupGroup</code></a> and
|
|
<a href="/pkg/os/user/#LookupGroupId"><code>LookupGroupId</code></a>
|
|
and the new field <code>GroupIds</code> in the <code>User</code> struct,
|
|
provides access to system-specific user group information.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
Although
|
|
<a href="/pkg/reflect/#Value"><code>Value</code></a>'s
|
|
<a href="/pkg/reflect/#Value.Field"><code>Field</code></a> method has always been documented to panic
|
|
if the given field number <code>i</code> is out of range, it has instead
|
|
silently returned a zero
|
|
<a href="/pkg/reflect/#Value"><code>Value</code></a>.
|
|
Go 1.7 changes the method to behave as documented.
|
|
</p>
|
|
|
|
<p>
|
|
The new
|
|
<a href="/pkg/reflect/#StructOf"><code>StructOf</code></a>
|
|
function constructs a struct type at run time.
|
|
It completes the set of type constructors, joining
|
|
<a href="/pkg/reflect/#ArrayOf"><code>ArrayOf</code></a>,
|
|
<a href="/pkg/reflect/#ChanOf"><code>ChanOf</code></a>,
|
|
<a href="/pkg/reflect/#FuncOf"><code>FuncOf</code></a>,
|
|
<a href="/pkg/reflect/#MapOf"><code>MapOf</code></a>,
|
|
<a href="/pkg/reflect/#PtrTo"><code>PtrTo</code></a>,
|
|
and
|
|
<a href="/pkg/reflect/#SliceOf"><code>SliceOf</code></a>.
|
|
</p>
|
|
|
|
<p>
|
|
<a href="/pkg/reflect/#StructTag"><code>StructTag</code></a>'s
|
|
new method
|
|
<a href="/pkg/reflect/#StructTag.Lookup"><code>Lookup</code></a>
|
|
is like
|
|
<a href="/pkg/reflect/#StructTag.Get"><code>Get</code></a>
|
|
but distinguishes the tag not containing the given key
|
|
from the tag associating an empty string with the given key.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/reflect/#Type.Method"><code>Method</code></a> and
|
|
<a href="/pkg/reflect/#Type.NumMethod"><code>NumMethod</code></a>
|
|
methods of
|
|
<a href="/pkg/reflect/#Type"><code>Type</code></a> and
|
|
<a href="/pkg/reflect/#Value"><code>Value</code></a>
|
|
no longer return or count unexported methods.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="strings"><dt><a href="/pkg/strings/">strings</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
In previous releases of Go, if
|
|
<a href="/pkg/strings/#Reader"><code>Reader</code></a>'s
|
|
<a href="/pkg/strings/#Reader.Read"><code>Read</code></a> method
|
|
were asked for zero bytes with no data remaining, it would
|
|
return a count of 0 and no error.
|
|
Now it returns a count of 0 and the error
|
|
<a href="/pkg/io/#EOF"><code>io.EOF</code></a>.
|
|
</p>
|
|
|
|
<p>
|
|
The
|
|
<a href="/pkg/strings/#Reader"><code>Reader</code></a> type has a new method
|
|
<a href="/pkg/strings/#Reader.Reset"><code>Reset</code></a> to allow reuse of a <code>Reader</code>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="time"><dt><a href="/pkg/time/">time</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
<a href="/pkg/time/#Duration"><code>Duration</code></a>'s
|
|
time.Duration.String method now reports the zero duration as <code>"0s"</code>, not <code>"0"</code>.
|
|
<a href="/pkg/time/#ParseDuration"><code>ParseDuration</code></a> continues to accept both forms.
|
|
</p>
|
|
|
|
<p>
|
|
The method call <code>time.Local.String()</code> now returns <code>"Local"</code> on all systems;
|
|
in earlier releases, it returned an empty string on Windows.
|
|
</p>
|
|
|
|
<p>
|
|
The time zone database in
|
|
<code>$GOROOT/lib/time</code> has been updated
|
|
to IANA release 2016d.
|
|
This fallback database is only used when the system time zone database
|
|
cannot be found, for example on Windows.
|
|
The Windows time zone abbreviation list has also been updated.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<dl id="syscall"><dt><a href="/pkg/syscall/">syscall</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
On Linux, the
|
|
<a href="/pkg/syscall/#SysProcAttr"><code>SysProcAttr</code></a> struct
|
|
(as used in
|
|
<a href="/pkg/os/exec/#Cmd"><code>os/exec.Cmd</code></a>'s <code>SysProcAttr</code> field)
|
|
has a new <code>Unshareflags</code> field.
|
|
If the field is nonzero, the child process created by
|
|
<a href="/pkg/syscall/#ForkExec"><code>ForkExec</code></a>
|
|
(as used in <code>exec.Cmd</code>'s <code>Run</code> method)
|
|
will call the
|
|
<a href="http://man7.org/linux/man-pages/man2/unshare.2.html"><i>unshare</i>(2)</a>
|
|
system call before executing the new program.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
|
|
<dl id="unicode"><dt><a href="/pkg/unicode/">unicode</a></dt>
|
|
|
|
<dd>
|
|
<p>
|
|
The <a href="/pkg/unicode/"><code>unicode</code></a> package and associated
|
|
support throughout the system has been upgraded from version 8.0 to
|
|
<a href="http://www.unicode.org/versions/Unicode9.0.0/">Unicode 9.0</a>.
|
|
</p>
|
|
</dd>
|
|
</dl>
|