title: Golang rewrite http request body
body: <p>I'm writing an http interceptor in Golang on the server side. I can read the http request body from <code>r.Body</code>. Now If I want to modify the body content, how can I modify the request body before the control is passed to the next interceptor?</p>
  
  <pre><code>func(w http.ResponseWriter, r *http.Request) {
      // Now I want to modify the request body, and 
      // handle(w, r)
  }
  </code></pre>