208 lines
7.1 KiB
Plaintext
208 lines
7.1 KiB
Plaintext
<!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: Goroutines</title>
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<div class="example" id="goroutines">
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<h2><a href="./">Go by Example</a>: Goroutines</h2>
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<table>
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<tr>
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<td class="docs">
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<p>A <em>goroutine</em> is a lightweight thread of execution.</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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<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/RW_RSAHfj-"><img title="Run code" src="play.png" class="run" /></a>
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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="s">"fmt"</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">f</span><span class="p">(</span><span class="nx">from</span> <span class="kt">string</span><span class="p">)</span> <span class="p">{</span>
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<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"><</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">i</span><span class="o">++</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="nx">from</span><span class="p">,</span> <span class="s">":"</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
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<span class="p">}</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>Suppose we have a function call <code>f(s)</code>. Here’s how
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we’d call that in the usual way, running it
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synchronously.</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">f</span><span class="p">(</span><span class="s">"direct"</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>To invoke this function in a goroutine, use
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<code>go f(s)</code>. This new goroutine will execute
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concurrently with the calling one.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">go</span> <span class="nx">f</span><span class="p">(</span><span class="s">"goroutine"</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>You can also start a goroutine for an anonymous
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function call.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">go</span> <span class="kd">func</span><span class="p">(</span><span class="nx">msg</span> <span class="kt">string</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">Println</span><span class="p">(</span><span class="nx">msg</span><span class="p">)</span>
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<span class="p">}(</span><span class="s">"going"</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>Our two function calls are running asynchronously in
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separate goroutines now, so execution falls through
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to here. This <code>Scanln</code> code requires we press a key
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before the program exits.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">input</span> <span class="kt">string</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Scanln</span><span class="p">(</span><span class="o">&</span><span class="nx">input</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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<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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<p>When we run this program, we see the output of the
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blocking call first, then the interleaved output of the
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two gouroutines. This interleaving reflects the
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goroutines being run concurrently by the Go runtime.</p>
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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 goroutines.go
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<span class="go">direct : 0</span>
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<span class="go">direct : 1</span>
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<span class="go">direct : 2</span>
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<span class="go">goroutine : 0</span>
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<span class="go">going</span>
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<span class="go">goroutine : 1</span>
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<span class="go">goroutine : 2</span>
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<span class="go"><enter></span>
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<span class="go">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>Next we’ll look at a complement to goroutines in
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concurrent Go programs: channels.</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="channels">Channels</a>.
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</p>
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<p class="footer">
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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/goroutines">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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