go/doc/go1.15.html

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<h2 id="introduction">DRAFT RELEASE NOTES — Introduction to Go 1.15</h2>

<p>
  <strong>
    Go 1.15 is not yet released. These are work-in-progress
    release notes. Go 1.15 is expected to be released in August 2020.
  </strong>
</p>

<h2 id="language">Changes to the language</h2>

<p>
TODO
</p>

<h2 id="ports">Ports</h2>

<p>
TODO
</p>

<h2 id="tools">Tools</h2>

<p>
TODO
</p>

<h3 id="go-command">Go command</h3>

<p><!-- golang.org/issue/37367 -->
  The <code>GOPROXY</code> environment variable now supports skipping proxies
  that return errors. Proxy URLs may now be separated with either commas
  (<code>,</code>) or pipe characters (<code>|</code>). If a proxy URL is
  followed by a comma, the <code>go</code> command will only try the next proxy
  in the list after a 404 or 410 HTTP response. If a proxy URL is followed by a
  pipe character, the <code>go</code> command will try the next proxy in the
  list after any error. Note that the default value of <code>GOPROXY</code>
  remains <code>https://proxy.golang.org,direct</code>, which does not fall
  back to <code>direct</code> in case of errors.
</p>

<p>
TODO
</p>

<h4 id="go-test"><code>go</code> <code>test</code></h4>

<p><!-- https://golang.org/issue/36134 -->
  Changing the <code>-timeout</code> flag now invalidates cached test results. A
  cached result for a test run with a long timeout will no longer count as
  passing when <code>go</code> <code>test</code> is re-invoked with a short one.
</p>

<h4 id="go-flag-parsing">Flag parsing</h4>

<p><!-- https://golang.org/cl/211358 -->
  Various flag parsing issues in <code>go</code> <code>test</code> and
  <code>go</code> <code>vet</code> have been fixed. Notably, flags specified
  in <code>GOFLAGS</code> are handled more consistently, and
  the <code>-outputdir</code> flag now interprets relative paths relative to the
  working directory of the <code>go</code> command (rather than the working
  directory of each individual test).
</p>

<h2 id="runtime">Runtime</h2>

<p>
TODO
</p>

<h2 id="compiler">Compiler</h2>

<p><!-- https://golang.org/cl/229578 -->
  Package <code>unsafe</code>'s <a href="/pkg/unsafe/#Pointer">safety
  rules</a> allow converting an <code>unsafe.Pointer</code>
  into <code>uintptr</code> when calling certain
  functions. Previously, in some cases, the compiler allowed multiple
  chained conversions (for example, <code>syscall.Syscall(…,
  uintptr(uintptr(ptr)), …)</code>). The compiler now requires exactly
  one conversion. Code that used multiple conversions should be
  updated to satisfy the safety rules.
</p>

<h2 id="library">Core library</h2>

<h3 id="time/tzdata">New embedded tzdata package</h3>

<p> <!-- CL 224588 -->
  Go 1.15 includes a new package,
  <a href="/pkg/time/tzdata/"><code>time/tzdata</code></a>,
  that permits embedding the timezone database into a program.
  Importing this package (as <code>import _ "time/tzdata"</code>)
  permits the program to find timezone information even if the
  timezone database is not available on the local system.
  You can also embed the timezone database by building
  with <code>-tags timetzdata</code>.
  Either approach increases the size of the program by about 800 KB.
</p>

<p>
TODO
</p>

<dl id="testing"><dt><a href="/pkg/testing/">testing</a></dt>
  <dd>
    <p><!-- golang.org/issue/28135 -->
      The <code>testing.T</code> type now has a <code>Deadline</code> method
      that reports the time at which the test binary will have exceeded its
      timeout.
    </p>
    <p><!-- golang.org/issue/34129 -->
      A <code>TestMain</code> function is no longer required to call
      <code>os.Exit</code>. If a <code>TestMain</code> function returns,
      the test binary will call <code>os.Exit</code> with the value returned
      by <code>m.Run</code>.
    </p>
  </dd>
</dl><!-- testing -->

<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>

<p>
TODO
</p>

<dl id="crypto/tls"><dt><a href="/crypto/tls/">crypto/tls</a></dt>
  <dd>
    <p><!-- CL 214977 -->
      The new
      <a href="/pkg/crypto/tls/#Dialer"><code>Dialer</code></a>
      type and its
      <a href="/pkg/crypto/tls/#Dialer.DialContext"><code>DialContext</code></a>
      method permits using a context to both connect and handshake with a TLS server.
    </p>
  </dd>
</dl>

<dl id="flag"><dt><a href="/pkg/flag/">flag</a></dt>
  <dd>
    <p><!-- CL 221427 -->
      When the flag package sees <code>-h</code> or <code>-help</code>, and
      those flags are not defined, the flag package prints a usage message.
      If the <a href="/pkg/flag/#FlagSet"><code>FlagSet</code></a> was created with
      <a href="/pkg/flag/#ExitOnError"><code>ExitOnError</code></a>,
      <a href="/pkg/flag/#FlagSet.Parse"><code>FlagSet.Parse</code></a> would then
      exit with a status of 2. In this release, the exit status for <code>-h</code>
      or <code>-help</code> has been changed to 0. In particular, this applies to
      the default handling of command line flags.
    </p>
  </dd>
</dl>

<dl id="net"><dt><a href="/pkg/net/">net</a></dt>
  <dd>
    <p><!-- CL -->
      If an I/O operation exceeds a deadline set by
      the <a href="/pkg/net/#Conn"><code>Conn.SetDeadline</code></a>,
      <code>Conn.SetReadDeadline</code>,
      or <code>Conn.SetWriteDeadline</code> methods, it will now
      return an error that is or wraps
      <a href="/pkg/os#ErrDeadlineExceeded"><code>os.ErrDeadlineExceeded</code></a>.
      This may be used to reliably detect whether an error is due to
      an exceeded deadline.
      Earlier releases recommended calling the <code>Timeout</code>
      method on the error, but I/O operations can return errors for
      which <code>Timeout</code> returns <code>true</code> although a
      deadline has not been exceeded.
    </p>
  </dd>
</dl>

<dl id="net/http/pprof"><dt><a href="/pkg/net/http/pprof/">net/http/pprof</a></dt>
  <dd>
    <p><!-- CL 147598, 229537 -->
      All profile endpoints now support a "seconds" parameter. When present,
      the endpoint profiles for the specified number of seconds and reports the difference.
      The meaning of the "seconds" parameter in the <code>cpu</code> profile and
      the trace endpoints is unchanged.
    </p>
  </dd>
</dl>

<dl id="net/url"><dt><a href="/pkg/net/url/">net/url</a></dt>
  <dd>
    <p><!-- CL 227645 -->
      The new <a href="/pkg/net/url/#URL"><code>URL</code></a> field
      <code>RawFragment</code> and method <a href="/pkg/net/url/#URL.EscapedFragment"><code>EscapedFragment</code></a>
      provide detail about and control over the exact encoding of a particular fragment.
      These are analogous to
      <code>RawPath</code> and <a href="/pkg/net/url/#URL.EscapedPath"><code>EscapedPath</code></a>.
    </p>
    <p><!-- CL 207082 -->
      The new <a href="/pkg/net/url/#URL"><code>URL</code></a>
      method <a href="/pkg/net/url/#URL.Redacted"><code>Redacted</code></a>
      returns the URL in string form with any password replaced with <code>xxxxx</code>.
    </p>
  </dd>
</dl>

<dl id="os"><dt><a href="/pkg/os/">os</a></dt>
  <dd>
    <p><!-- CL -->
      If an I/O operation exceeds a deadline set by
      the <a href="/pkg/os/#File.SetDeadline"><code>File.SetDeadline</code></a>,
      <a href="/pkg/os/#File.SetReadDeadline"><code>File.SetReadDeadline</code></a>,
      or <a href="/pkg/os/#File.SetWriteDeadline"><code>File.SetWriteDeadline</code></a>
      methods, it will now return an error that is or wraps
      <a href="/pkg/os#ErrDeadlineExceeded"><code>os.ErrDeadlineExceeded</code></a>.
      This may be used to reliably detect whether an error is due to
      an exceeded deadline.
      Earlier releases recommended calling the <code>Timeout</code>
      method on the error, but I/O operations can return errors for
      which <code>Timeout</code> returns <code>true</code> although a
      deadline has not been exceeded.
    </p>
  </dd>
</dl>

<dl id="reflect"><dt><a href="/pkg/reflect/">reflect</a></dt>
  <dd>
    <p><!-- CL 228902 -->
      Package reflect now disallows accessing methods of all
      non-exported fields, whereas previously it allowed accessing
      those of non-exported, embedded fields. Code that relies on the
      previous behavior should be updated to instead access the
      corresponding promoted method of the enclosing variable.
    </p>
  </dd>
</dl>

<dl id="pkg-runtime"><dt><a href="/pkg/runtime/">runtime</a></dt>
  <dd>
    <p><!-- CL 221779 -->
      If <code>panic</code> is invoked with a value whose type is derived from any
      of: <code>bool</code>, <code>complex64</code>, <code>complex128</code>, <code>float32</code>, <code>float64</code>,
      <code>int</code>, <code>int8</code>, <code>int16</code>, <code>int32</code>, <code>int64</code>, <code>string</code>,
      <code>uint</code>, <code>uint8</code>, <code>uint16</code>, <code>uint32</code>, <code>uint64</code>, <code>uintptr</code>,
      then the value will be printed, instead of just its address.
    </p>

    <p><!-- CL -->
      On a Unix system, if the <code>kill</code> command
      or <code>kill</code> system call is used to send
      a <code>SIGSEGV</code>, <code>SIGBUS</code>,
      or <code>SIGFPE</code> signal to a Go program, and if the signal
      is not being handled via
      <a href="/pkg/os/signal/#Notify"><code>os/signal.Notify</code></a>,
      the Go program will now reliably crash with a stack trace.
      In earlier releases the behavior was unpredictable.
    </p>
  </dd>
</dl>

<dl id="pkg-runtime-pprof"><dt><a href="/pkg/runtime/pprof">runtime/pprof</a></dt>
  <dd>
    <p><!-- CL 189318 -->
      The goroutine profile includes the profile labels associated with each goroutine
      at the time of profiling. This feature is not yet implemented for the profile
      reported with <code>debug=2</code>.
    </p>
  </dd>
</dl>

<dl id="sync"><dt><a href="/pkg/sync/">sync</a></dt>
  <dd>
    <p><!-- CL 205899, golang.org/issue/33762 -->
      The new method
      <a href="/pkg/sync/#Map.LoadAndDelete"><code>Map.LoadAndDelete</code></a>
      atomically deletes a key and returns the previous value if present.
    </p>
    <p><!-- CL 205899 -->
      The method
      <a href="/pkg/sync/#Map.Delete"><code>Map.Delete</code></a>
      is more efficient.
    </p>
</dl><!-- sync -->

<dl id="testing"><dt><a href="/pkg/testing/">testing</a></dt>
  <dd>
    <p><!-- CL 226877, golang.org/issue/35998 -->
       The new methods
       <a href="/pkg/testing/#T.TempDir"><code>T.TempDir</code></a> and
       <a href="/pkg/testing/#B.TempDir"><code>B.TempDir</code></a> and
       return temporary directories that are automatically cleaned up
       at the end of the test.
    </p>
  </dd>
</dl><!-- testing -->

<dl id="time"><dt><a href="/pkg/time/">time</a></dt>
  <dd>
    <p><!-- CL 220424, CL 217362, golang.org/issue/33184 -->
       The new method
       <a href="/pkg/time/#Ticker.Reset"><code>Ticker.Reset</code></a>
       supports changing the duration of a ticker.
    </p>
  </dd>
</dl><!-- time -->