Writing to multiple outputs (io.Multiwriter?)

<p>Say I want to take data coming in as a http request and simultaneously write it to multiple places (e. g. to file, to s3, to some cache etc). </p> <p>What is the best pattern in go for doing that? </p> <p>Would be nice to avoid loading the data into memory in full as it can be quite large at times</p> <hr/>**评论：**<br/><br/>The_Sly_Marbo: <pre><p>As your title suggests, you want to use <code>io.MultiWriter</code> to collect your outputs together, then use <code>io.Copy</code> to copy from you input (the request body) into the multi writer.</p></pre>joeyGibson: <pre><p><code>io.MultiWriter</code> is the way to go. This is a snippet of some code I wrote recently. I needed to copy a file into an HTTP form to <code>POST</code>, but I also needed to compute a SHA256 hash of the file. <code>MultiWriter</code> solved it nicely. (Note: In the actual code, I&#39;m not ignoring the <code>error</code> returns. I removed them for this post, for brevity.)</p> <pre><code>sha := sha256.New() file, _ := os.Open(pathName) defer file.Close() var b bytes.Buffer w := multipart.NewWriter(&amp;b) _, fileName := path.Split(pathName) fw, _ := w.CreateFormFile(&#34;file&#34;, fileName) // Create the MultiWriter to write to both writers multiWriter := io.MultiWriter(sha, fw) // Efficiently copy the file to both writers io.Copy(multiWriter, file) hash := sha.Sum(nil) logger.Infof(&#34;%s -&gt; %x&#34;, pathName, hash) </code></pre></pre>