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fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">Go by example</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">Panic and Recover</span><meta itemprop="position" content="2"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><h1>Panic and Recover</h1><h2 class="anchor anchorWithStickyNavbar_LWe7" id="panic">Panic<a href="#panic" class="hash-link" aria-label="Direct link to Panic" title="Direct link to Panic"></a></h2><p><code>panic</code> is used whenever our application can no longer function. In Go it's mostly left up to the developer to decide when an error is a problem in your application.
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<code>panic</code> helps you tell your program it encountered a fatal problem which can not be recovered. Panic always prints a stack trace to help locate the problematic line of code.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="panic-and-defer">Panic and Defer<a href="#panic-and-defer" class="hash-link" aria-label="Direct link to Panic and Defer" title="Direct link to Panic and Defer"></a></h2><div class="language-go codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#bfc7d5;--prism-background-color:#292d3e"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-go codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#bfc7d5"><span class="token keyword" style="font-style:italic">func</span><span class="token plain"> </span><span class="token function" style="color:rgb(130, 170, 255)">main</span><span class="token punctuation" style="color:rgb(199, 146, 234)">(</span><span class="token punctuation" style="color:rgb(199, 146, 234)">)</span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(199, 146, 234)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> fmt</span><span class="token punctuation" style="color:rgb(199, 146, 234)">.</span><span class="token function" style="color:rgb(130, 170, 255)">Println</span><span class="token punctuation" style="color:rgb(199, 146, 234)">(</span><span class="token string" style="color:rgb(195, 232, 141)">"Start"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token keyword" style="font-style:italic">defer</span><span class="token plain"> fmt</span><span class="token punctuation" style="color:rgb(199, 146, 234)">.</span><span class="token function" style="color:rgb(130, 170, 255)">Println</span><span class="token punctuation" style="color:rgb(199, 146, 234)">(</span><span class="token string" style="color:rgb(195, 232, 141)">"Deferred"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> </span><span class="token function" style="color:rgb(130, 170, 255)">panic</span><span class="token punctuation" style="color:rgb(199, 146, 234)">(</span><span class="token string" style="color:rgb(195, 232, 141)">"Panic"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"> fmt</span><span class="token punctuation" style="color:rgb(199, 146, 234)">.</span><span class="token function" style="color:rgb(130, 170, 255)">Println</span><span class="token punctuation" style="color:rgb(199, 146, 234)">(</span><span class="token string" style="color:rgb(195, 232, 141)">"End"</span><span class="token punctuation" style="color:rgb(199, 146, 234)">)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#bfc7d5"><span class="token plain"></span><span class="token punctuation" style="color:rgb(199, 146, 234)">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>The above code will print: 'Start', 'Deferred' and then 'Panic'. This is because defer statements will always be executed even in case of a panic.
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So the order of execution is: Execute called function, then execute defer statements, and in case of a panic program execution will stop.
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So even if your application will panic defer statements are handled and therefore resources will be closed accordingly.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="panic-and-recover-1">Panic and Recover<a href="#panic-and-recover-1" class="hash-link" aria-label="Direct link to Panic and Recover" title="Direct link to Panic and Recover"></a></h2><p>Try out the following example: </p><div style="padding-bottom:1rem;width:100%"><button class="button button--primary">open playground</button> <a href="https://goplay.tools/snippet/BN8Boz9LRVX" target="_blank" rel="noopener noreferrer">go to <!-- -->https://goplay.tools/snippet/BN8Boz9LRVX</a></div><pre class="prism-code language-go" style="background-color:#2a2734;color:#9a86fd">... loading sources<div class="token-line" style="color:#9a86fd"><span class="token plain" style="display:inline-block">
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</span></div></pre><div style="display:none"><div><button class="button button--lg button--secondary">load external go playground, with all it´s potentially evil cookies coming from https://goplay.tools</button></div></div>The function that panics will stop because it can no longer function so we don't see 'Is this printed?' printed. The recover function makes it possible to obtain the error in case a panic occurred, and leaves the decision how to proceed to the programmer. In this example, we decided to just log the error and continue to run. The function that panicked will stop execution at the panic, but the code that called it will continue to execute, which is why we see 'End' being printed.</div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-tags-row row margin-bottom--sm"><div class="col"><b>Tags:</b><ul class="tags_jXut padding--none margin-left--sm"><li class="tag_QGVx"><a class="tag_zVej tagRegular_sFm0" href="/docs/tags/go-basics">Go Basics</a></li></ul></div></div><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/foomo/foomo-docs/tree/main/foomo/docs/backend/go-by-example/panic-and-recover.mdx" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages"><a class="pagination-nav__link pagination-nav__link--prev" href="/docs/backend/go-by-example/defer"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Defer</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/backend/go-by-example/nil-maps"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Maps</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ul class="table-of-contents table-of-contents__left-border"><li><a href="#panic" class="table-of-contents__link toc-highlight">Panic</a></li><li><a href="#panic-and-defer" class="table-of-contents__link toc-highlight">Panic and Defer</a></li><li><a href="#panic-and-recover-1" class="table-of-contents__link toc-highlight">Panic and Recover</a></li></ul></div></div></div></div></main></div></div><footer class="footer"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title">github</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://github.com/foomo" target="_blank" rel="noopener noreferrer" class="footer__link-item">https://github.com/foomo</a></li></ul></div><div class="col footer__col"><div class="footer__title">legal</div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/etc/imprint">Imprint</a></li></ul></div></div><div class="footer__bottom text--center"><div class="footer__copyright">© 2023 bestbytes</div></div></div></footer></div>
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