panic

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      <h2><a href="./">Go by Example</a>: Panic</h2>

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            <p>A <code>panic</code> typically means something went unexpectedly
wrong. Mostly we use it to fail fast on errors that
shouldn&rsquo;t occur during normal operation, or that we
aren&rsquo;t prepared to handle gracefully.</p>

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            <div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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            <div class="highlight"><pre><span class="kn">import</span> <span class="s">&quot;os&quot;</span>
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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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            <p>We&rsquo;ll use panic throughout this site to check for
unexpected errors. This is the only program on the
site designed to panic.</p>

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            <div class="highlight"><pre>    <span class="nb">panic</span><span class="p">(</span><span class="s">&quot;a problem&quot;</span><span class="p">)</span>
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            <p>A common use of panic is to abort if a function
returns an error value that we don&rsquo;t know how to
(or want to) handle. Here&rsquo;s an example of
<code>panic</code>king if we get an unexpected error when creating a new file.</p>

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            <div class="highlight"><pre>    <span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nx">Create</span><span class="p">(</span><span class="s">&quot;/tmp/file&quot;</span><span class="p">)</span>
    <span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
        <span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
    <span class="p">}</span>
<span class="p">}</span>
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            <p>Running this program will cause it to panic, print
an error message and goroutine traces, and exit with
a non-zero status.</p>

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            <div class="highlight"><pre><span class="gp">$</span> go run panic.go
<span class="go">panic: a problem</span>
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            <div class="highlight"><pre><span class="go">goroutine 1 [running]:</span>
<span class="go">main.main()</span>
<span class="go">	/.../panic.go:12 +0x47</span>
<span class="go">...</span>
<span class="go">exit status 2</span>
</pre></div>

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            <p>Note that unlike some languages which use exceptions
for handling of many errors, in Go it is idiomatic
to use error-indicating return values wherever possible.</p>

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