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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.
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192 lines
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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: Timers</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 = 'range-over-channels';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'tickers';
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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="timers">
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<h2><a href="./">Go by Example</a>: Timers</h2>
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<table>
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<tr>
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<td class="docs">
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<p>We often want to execute Go code at some point in the
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future, or repeatedly at some interval. Go’s built-in
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<em>timer</em> and <em>ticker</em> features make both of these tasks
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easy. We’ll look first at timers and then
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at <a href="tickers">tickers</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/gF7VLRz3URM"><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>Timers represent a single event in the future. You
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tell the timer how long you want to wait, and it
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provides a channel that will be notified at that
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time. This timer will wait 2 seconds.</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">timer1</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">NewTimer</span><span class="p">(</span><span class="mi">2</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Second</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>The <code><-timer1.C</code> blocks on the timer’s channel <code>C</code>
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until it sends a value indicating that the timer
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fired.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="o"><-</span><span class="nx">timer1</span><span class="p">.</span><span class="nx">C</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">"Timer 1 fired"</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>If you just wanted to wait, you could have used
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<code>time.Sleep</code>. One reason a timer may be useful is
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that you can cancel the timer before it fires.
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Here’s an example of that.</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">timer2</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">NewTimer</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="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
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<span class="o"><-</span><span class="nx">timer2</span><span class="p">.</span><span class="nx">C</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">"Timer 2 fired"</span><span class="p">)</span>
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<span class="p">}()</span>
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<span class="nx">stop2</span> <span class="o">:=</span> <span class="nx">timer2</span><span class="p">.</span><span class="nx">Stop</span><span class="p">()</span>
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<span class="k">if</span> <span class="nx">stop2</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">"Timer 2 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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<tr>
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<td class="docs">
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<p>Give the <code>timer2</code> enough time to fire, if it ever
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was going to, to show it is in fact stopped.</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">2</span> <span class="o">*</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="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>The first timer will fire ~2s after we start the
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program, but the second should be stopped before it has
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a chance to fire.</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 timers.go
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<span class="go">Timer 1 fired</span>
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<span class="go">Timer 2 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="tickers">Tickers</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/timers">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(' timer1 :\u003D time.NewTimer(2 * time.Second)\u000A');codeLines.push(' \u003C-timer1.C\u000A fmt.Println(\"Timer 1 fired\")\u000A');codeLines.push(' timer2 :\u003D time.NewTimer(time.Second)\u000A go func() {\u000A \u003C-timer2.C\u000A fmt.Println(\"Timer 2 fired\")\u000A }()\u000A stop2 :\u003D timer2.Stop()\u000A if stop2 {\u000A fmt.Println(\"Timer 2 stopped\")\u000A }\u000A');codeLines.push(' time.Sleep(2 * time.Second)\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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