yeray/gobyexample
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
gobyexample/public/select
Hana 9e216da9ef go.mod: add go.mod and move pygments to third_party 
After go1.16, go will use module mode by default,
even when the repository is checked out under GOPATH
or in a one-off directory. Add go.mod, go.sum to keep
this repo buildable without opting out of the module
mode.

> go mod init github.com/mmcgrana/gobyexample
> go mod tidy
> go mod vendor

In module mode, the 'vendor' directory is special
and its contents will be actively maintained by the
go command. pygments aren't the dependency the go will
know about, so it will delete the contents from vendor
directory. Move it to `third_party` directory now.

And, vendor the blackfriday package.

Note: the tutorial contents are not affected by the
change in go1.16 because all the examples in this
tutorial ask users to run the go command with the
explicit list of files to be compiled (e.g.
`go run hello-world.go` or `go build command-line-arguments.go`).
When the source list is provided, the go command does
not have to compute the build list and whether it's
running in GOPATH mode or module mode becomes irrelevant.
2021-02-15 16:45:26 -05:00

191 lines
7.8 KiB
Plaintext
Generated
Raw Blame History

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: Select</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'channel-directions';
}
if (e.key == "ArrowRight") {
window.location.href = 'timeouts';
}
}
</script>
<body>
<div class="example" id="select">
<h2><a href="./">Go by Example</a>: Select</h2>
<table>
<tr>
<td class="docs">
<p>Go&rsquo;s <em>select</em> lets you wait on multiple channel
operations. Combining goroutines and channels with
select is a powerful feature of Go.</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="http://play.golang.org/p/FzONhs4-tae"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
<span class="s">&quot;fmt&quot;</span>
<span class="s">&quot;time&quot;</span>
<span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>For our example we&rsquo;ll select across two channels.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="nx">c1</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">)</span>
<span class="nx">c2</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">)</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Each channel will receive a value after some amount
of time, to simulate e.g. blocking RPC operations
executing in concurrent goroutines.</p>
</td>
<td class="code leading">
<div class="highlight"><pre> <span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">time</span><span class="p">.</span><span class="nx">Sleep</span><span class="p">(</span><span class="mi">1</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
<span class="nx">c1</span> <span class="o">&lt;-</span> <span class="s">&quot;one&quot;</span>
<span class="p">}()</span>
<span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">time</span><span class="p">.</span><span class="nx">Sleep</span><span class="p">(</span><span class="mi">2</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
<span class="nx">c2</span> <span class="o">&lt;-</span> <span class="s">&quot;two&quot;</span>
<span class="p">}()</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>We&rsquo;ll use <code>select</code> to await both of these values
simultaneously, printing each one as it arrives.</p>
</td>
<td class="code">
<div class="highlight"><pre> <span class="k">for</span> <span class="nx">i</span> <span class="o">:=</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">i</span> <span class="p">&lt;</span> <span class="mi">2</span><span class="p">;</span> <span class="nx">i</span><span class="o">++</span> <span class="p">{</span>
<span class="k">select</span> <span class="p">{</span>
<span class="k">case</span> <span class="nx">msg1</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="nx">c1</span><span class="p">:</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;received&quot;</span><span class="p">,</span> <span class="nx">msg1</span><span class="p">)</span>
<span class="k">case</span> <span class="nx">msg2</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="nx">c2</span><span class="p">:</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">&quot;received&quot;</span><span class="p">,</span> <span class="nx">msg2</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>We receive the values <code>&quot;one&quot;</code> and then <code>&quot;two&quot;</code> as
expected.</p>
</td>
<td class="code leading">
<div class="highlight"><pre><span class="gp">$</span> <span class="nb">time</span> go run <span class="k">select</span>.go
<span class="go">received one</span>
<span class="go">received two</span>
</pre></div>
</td>
</tr>
<tr>
<td class="docs">
<p>Note that the total execution time is only ~2 seconds
since both the 1 and 2 second <code>Sleeps</code> execute
concurrently.</p>
</td>
<td class="code">
<div class="highlight"><pre><span class="go">real 0m2.245s</span>
</pre></div>
</td>
</tr>
</table>
<p class="next">
Next example: <a href="timeouts">Timeouts</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/select">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
<script>
var codeLines = [];
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"time\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' c1 :\u003D make(chan string)\u000A c2 :\u003D make(chan string)\u000A');codeLines.push(' go func() {\u000A time.Sleep(1 * time.Second)\u000A c1 \u003C- \"one\"\u000A }()\u000A go func() {\u000A time.Sleep(2 * time.Second)\u000A c2 \u003C- \"two\"\u000A }()\u000A');codeLines.push(' for i :\u003D 0; i \u003C 2; i++ {\u000A select {\u000A case msg1 :\u003D \u003C-c1:\u000A fmt.Println(\"received\", msg1)\u000A case msg2 :\u003D \u003C-c2:\u000A fmt.Println(\"received\", msg2)\u000A }\u000A }\u000A}\u000A');codeLines.push('');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink