title: get notified when http.Server starts listening
body: <p>When I look at the net/http server interface, I don't see an obvious way to get notified and react when the http.Server comes up and <strong>starts</strong> listening:</p>
  
  <pre><code>ListenAndServe(":8080", nil)
  </code></pre>
  
  <p>The function doesn't return until the server actually shuts down. I also looked at the Server type, but there doesn't appear to be anything that lets me tap into that timing. Some function or a channel would have been great but I don't see any.</p>
  
  <p>Is there any way that will let me detect that event, or am I left to just sleeping "enough" to fake it?</p>