| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Requires a `Future` to complete before the specified duration has elapsed."><meta name="keywords" content="rust, rustlang, rust-lang, timeout"><title>timeout in tokio::time - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin 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class="sidebar-menu-toggle">☰</button><a class="sidebar-logo" href="../../tokio/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><h2></h2></nav><nav class="sidebar"><a class="sidebar-logo" href="../../tokio/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a><div class="sidebar-elems"><h2><a href="index.html">In tokio::time</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1 class="fqn">Function <a href="../index.html">tokio</a>::<wbr><a href="index.html">time</a>::<wbr><a class="fn" href="#">timeout</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="srclink" href="../../src/tokio/time/timeout.rs.html#86-98">source</a> · <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span></div><div class="item-decl"><pre class="rust fn"><code>pub fn timeout<F>(duration: <a class="struct" href="https://doc.rust-lang.org/nightly/core/time/struct.Duration.html" title="struct core::time::Duration">Duration</a>, future: F) -> <a class="struct" href="struct.Timeout.html" title="struct tokio::time::Timeout">Timeout</a><F><span class="notable-traits"><span class="notable-traits-tooltip">ⓘ<span class="notable-traits-tooltiptext"><span class="docblock"><span class="notable">Notable traits for <a class="struct" href="struct.Timeout.html" title="struct tokio::time::Timeout">Timeout</a><T></span><code class="content"><span class="where fmt-newline">impl<T> <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a> for <a class="struct" href="struct.Timeout.html" title="struct tokio::time::Timeout">Timeout</a><T><span class="where fmt-newline">where<br> T: <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a>,</span></span><span class="where fmt-newline"> type <a href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html#associatedtype.Output" class="associatedtype">Output</a> = <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a><T::<a class="associatedtype" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html#associatedtype.Output" title="type core::future::future::Future::Output">Output</a>, <a class="struct" href="error/struct.Elapsed.html" title="struct tokio::time::error::Elapsed">Elapsed</a>>;</span></code></span></span></span></span><span class="where fmt-newline">where<br> F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/future/future/trait.Future.html" title="trait core::future::future::Future">Future</a>,</span></code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Requires a <code>Future</code> to complete before the specified duration has elapsed.</p> |
| <p>If the future completes before the duration has elapsed, then the completed |
| value is returned. Otherwise, an error is returned and the future is |
| canceled.</p> |
| <p>Note that the timeout is checked before polling the future, so if the future |
| does not yield during execution then it is possible for the future to complete |
| and exceed the timeout <em>without</em> returning an error.</p> |
| <p>This function returns a future whose return type is <a href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html"><code>Result</code></a><code><T,</code><a href="error/struct.Elapsed.html"><code>Elapsed</code></a><code>></code>, where <code>T</code> is the |
| return type of the provided future.</p> |
| <p>If the provided future completes immediately, then the future returned from |
| this function is guaranteed to complete immediately with an <a href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html#variant.Ok"><code>Ok</code></a> variant |
| no matter the provided duration.</p> |
| <h2 id="cancellation"><a href="#cancellation">Cancellation</a></h2> |
| <p>Cancelling a timeout is done by dropping the future. No additional cleanup |
| or other work is required.</p> |
| <p>The original future may be obtained by calling <a href="struct.Timeout.html#method.into_inner" title="Timeout::into_inner"><code>Timeout::into_inner</code></a>. This |
| consumes the <code>Timeout</code>.</p> |
| <h2 id="examples"><a href="#examples">Examples</a></h2> |
| <p>Create a new <code>Timeout</code> set to expire in 10 milliseconds.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tokio::time::timeout; |
| <span class="kw">use </span>tokio::sync::oneshot; |
| |
| <span class="kw">use </span>std::time::Duration; |
| |
| <span class="kw">let </span>(tx, rx) = oneshot::channel(); |
| |
| <span class="comment">// Wrap the future with a `Timeout` set to expire in 10 milliseconds. |
| </span><span class="kw">if let </span><span class="prelude-val">Err</span>(<span class="kw">_</span>) = timeout(Duration::from_millis(<span class="number">10</span>), rx).<span class="kw">await </span>{ |
| <span class="macro">println!</span>(<span class="string">"did not receive value within 10 ms"</span>); |
| }</code></pre></div> |
| <h2 id="panics"><a href="#panics">Panics</a></h2> |
| <p>This function panics if there is no current timer set.</p> |
| <p>It can be triggered when <a href="../runtime/struct.Builder.html#method.enable_time"><code>Builder::enable_time</code></a> or |
| <a href="../runtime/struct.Builder.html#method.enable_all"><code>Builder::enable_all</code></a> are not included in the builder.</p> |
| <p>It can also panic whenever a timer is created outside of a |
| Tokio runtime. That is why <code>rt.block_on(sleep(...))</code> will panic, |
| since the function is executed outside of the runtime. |
| Whereas <code>rt.block_on(async {sleep(...).await})</code> doesn’t panic. |
| And this is because wrapping the function on an async makes it lazy, |
| and so gets executed inside the runtime successfully without |
| panicking.</p> |
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