channels

<!DOCTYPE html>
<html>
  <head>
    <meta http-eqiv="content-type" content="text/html;charset=utf-8">
    <title>Go by Example: Channels</title>
    <link rel=stylesheet href="site.css">
  </head>
  <script type="text/javascript">
    if (window.location.host == "gobyexample.com") {
      var _gaq = _gaq || [];
      _gaq.push(['_setAccount', 'UA-34996217-1']);
      _gaq.push(['_trackPageview']);
      (function() {
        var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
        ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
        var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
      })();
    }
  </script>
  <body>
    <div class="example" id="channels">
      <h2><a href="./">Go by Example</a>: Channels</h2>

      <table>

        <tr>
          <td class="docs">
            <p><em>Channels</em> are the pipes that connect concurrent
goroutines. You can send values into channels from one
goroutine and receive those values into another
goroutine. Channels are a powerful primitive that
underly much of Go&rsquo;s functionality.</p>

          </td>
          <td class="code empty leading">

          </td>
        </tr>

        <tr>
          <td class="docs">

          </td>
          <td class="code leading">
            <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="s">&quot;fmt&quot;</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>Create a new channel with <code>make(chan val-type)</code>.
Channels are typed by the values they convey.</p>

          </td>
          <td class="code leading">
            <div class="highlight"><pre>    <span class="nx">messages</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><em>Send</em> a value into a channel using the <code>channel &lt;-</code>
syntax. Here we send <code>&quot;ping&quot;</code>  to the <code>messages</code>
channel we made above, from a new goroutine.</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">messages</span> <span class="o">&lt;-</span> <span class="s">&quot;ping&quot;</span> <span class="p">}()</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>The <code>&lt;-channel</code> syntax <em>receives</em> a value from the
channel. Here we&rsquo;ll receive the <code>&quot;ping&quot;</code> message
we sent above and print it out.</p>

          </td>
          <td class="code">
            <div class="highlight"><pre>    <span class="nx">msg</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="nx">messages</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">msg</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>

          </td>
        </tr>

      </table>

      <table>

        <tr>
          <td class="docs">
            <p>When we run the program the <code>&quot;ping&quot;</code> message is
succesfully passed from one goroutine to another via our
channel.</p>

          </td>
          <td class="code leading">
            <div class="highlight"><pre><span class="gp">$</span> go run channels.go
<span class="go">ping</span>
</pre></div>

          </td>
        </tr>

        <tr>
          <td class="docs">
            <p>By default sends and receives block until both the
sender and receiver are ready. This property allowed
us to wait at the end of our program for the <code>&quot;ping&quot;</code>
message without having to use any other synchronization.</p>

          </td>
          <td class="code empty">

          </td>
        </tr>

      </table>


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

      <p class="footer">
        <a href="https://twitter.com/gobyexample">@gobyexample</a> | <a href="mailto:mmcgrana@gmail.com">feedback</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/channels">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
      </p>
    </div>
  </body>
</html>