channel-synchronization

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    <div class="example" id="channel-synchronization">
      <h2><a href="./">Go by Example</a>: Channel Synchronization</h2>

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            <p>We can use channels to synchronize execution
across goroutines. Here&rsquo;s an example of using a
blocking receive to wait for a goroutine to finish.</p>

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	        <a href="http://play.golang.org/p/0DfW-1RMqi"><img title="Run code" src="play.png" class="run" /></a>
            <div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
</pre></div>

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            <div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;fmt&quot;</span>
<span class="kn">import</span> <span class="s">&quot;time&quot;</span>
</pre></div>

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            <p>This is the function we&rsquo;ll run in a goroutine. The
<code>done</code> channel will be used to notify another
goroutine that this function&rsquo;s work is done.</p>

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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>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Print</span><span class="p">(</span><span class="s">&quot;working...&quot;</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="nx">time</span><span class="p">.</span><span class="nx">Second</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;done&quot;</span><span class="p">)</span>
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            <p>Send a value to notify that we&rsquo;re done.</p>

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            <div class="highlight"><pre>    <span class="nx">done</span> <span class="o">&lt;-</span> <span class="kc">true</span>
<span class="p">}</span>
</pre></div>

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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>
</pre></div>

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            <p>Start a worker goroutine, giving it the channel to
notify on.</p>

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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>
    <span class="k">go</span> <span class="nx">worker</span><span class="p">(</span><span class="nx">done</span><span class="p">)</span>
</pre></div>

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            <p>Block until we receive a notification from the
worker on the channel.</p>

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            <div class="highlight"><pre>    <span class="o">&lt;-</span><span class="nx">done</span>
<span class="p">}</span>
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            <div class="highlight"><pre><span class="gp">$</span> go run channel-synchronization.go
<span class="go">working...done                  </span>
</pre></div>

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            <p>If you removed the <code>&lt;- done</code> line from this program, the
program would exit before the <code>worker</code> even
started.</p>

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      <p class="next">
        Next example: <a href="channel-directions">Channel Directions</a>.
      </p>

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        by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</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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