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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.
179 lines
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179 lines
7.1 KiB
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<!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: Tickers</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'timers';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'worker-pools';
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}
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}
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</script>
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<body>
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<div class="example" id="tickers">
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<h2><a href="./">Go by Example</a>: Tickers</h2>
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<table>
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<tr>
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<td class="docs">
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<p><a href="timers">Timers</a> are for when you want to do
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something once in the future - <em>tickers</em> are for when
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you want to do something repeatedly at regular
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intervals. Here’s an example of a ticker that ticks
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periodically until we stop it.</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/gs6zoJP-Pl9"><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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</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>Tickers use a similar mechanism to timers: a
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channel that is sent values. Here we’ll use the
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<code>select</code> builtin on the channel to await the
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values as they arrive every 500ms.</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">ticker</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">NewTicker</span><span class="p">(</span><span class="mi">500</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Millisecond</span><span class="p">)</span>
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<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>
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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="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">for</span> <span class="p">{</span>
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<span class="k">select</span> <span class="p">{</span>
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<span class="k">case</span> <span class="o"><-</span><span class="nx">done</span><span class="p">:</span>
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<span class="k">return</span>
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<span class="k">case</span> <span class="nx">t</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">ticker</span><span class="p">.</span><span class="nx">C</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">"Tick at"</span><span class="p">,</span> <span class="nx">t</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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<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>Tickers can be stopped like timers. Once a ticker
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is stopped it won’t receive any more values on its
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channel. We’ll stop ours after 1600ms.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">time</span><span class="p">.</span><span class="nx">Sleep</span><span class="p">(</span><span class="mi">1600</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Millisecond</span><span class="p">)</span>
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<span class="nx">ticker</span><span class="p">.</span><span class="nx">Stop</span><span class="p">()</span>
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<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</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">"Ticker stopped"</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 the ticker should tick 3 times
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before we stop it.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run tickers.go
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<span class="go">Tick at 2012-09-23 11:29:56.487625 -0700 PDT</span>
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<span class="go">Tick at 2012-09-23 11:29:56.988063 -0700 PDT</span>
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<span class="go">Tick at 2012-09-23 11:29:57.488076 -0700 PDT</span>
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<span class="go">Ticker stopped</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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<p class="next">
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Next example: <a href="worker-pools">Worker Pools</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/tickers">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 main() {\u000A');codeLines.push(' ticker :\u003D time.NewTicker(500 * time.Millisecond)\u000A done :\u003D make(chan bool)\u000A');codeLines.push(' go func() {\u000A for {\u000A select {\u000A case \u003C-done:\u000A return\u000A case t :\u003D \u003C-ticker.C:\u000A fmt.Println(\"Tick at\", t)\u000A }\u000A }\u000A }()\u000A');codeLines.push(' time.Sleep(1600 * time.Millisecond)\u000A ticker.Stop()\u000A done \u003C- true\u000A fmt.Println(\"Ticker stopped\")\u000A}\u000A');codeLines.push('');
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</script>
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<script src="site.js" async></script>
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</body>
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</html>
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