192 lines
6.4 KiB
Plaintext
Generated
192 lines
6.4 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Channel Synchronization</title>
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<link rel=stylesheet href="site.css">
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</head>
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<div class="example" id="channel-synchronization">
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<h2><a href="./">Go by Example</a>: Channel Synchronization</h2>
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<table>
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<tr>
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<td class="docs">
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<p>We can use channels to synchronize execution
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across goroutines. Here’s an example of using a
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blocking receive to wait for a goroutine to finish.
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When waiting for multiple goroutines to finish,
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you may prefer to use a <a href="waitgroups">WaitGroup</a>.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/Nw-1DzIGk5f"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"time"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>This is the function we’ll run in a goroutine. The
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<code>done</code> channel will be used to notify another
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goroutine that this function’s work is done.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">worker</span><span class="p">(</span><span class="nx">done</span> <span class="kd">chan</span> <span class="kt">bool</span><span class="p">)</span> <span class="p">{</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="s">"working..."</span><span class="p">)</span>
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<span class="nx">time</span><span class="p">.</span><span class="nx">Sleep</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="s">"done"</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Send a value to notify that we’re done.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Start a worker goroutine, giving it the channel to
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notify on.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">done</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">bool</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
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<span class="k">go</span> <span class="nx">worker</span><span class="p">(</span><span class="nx">done</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Block until we receive a notification from the
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worker on the channel.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="o"><-</span><span class="nx">done</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> go run channel-synchronization.go
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<span class="go">working...done </span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>If you removed the <code><- done</code> line from this program, the
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program would exit before the <code>worker</code> even
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started.</p>
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</td>
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<td class="code empty">
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="channel-directions">Channel Directions</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/channel-synchronization">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"time\"\u000A)\u000A');codeLines.push('func worker(done chan bool) {\u000A fmt.Print(\"working...\")\u000A time.Sleep(time.Second)\u000A fmt.Println(\"done\")\u000A');codeLines.push(' done \x3C- true\u000A}\u000A');codeLines.push('func main() {\u000A');codeLines.push(' done :\x3D make(chan bool, 1)\u000A go worker(done)\u000A');codeLines.push(' \x3C-done\u000A}\u000A');codeLines.push('');codeLines.push('');
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