title: Catch error on serveFile function from node-static
body: <p>Seems that the <a href="https://github.com/cloudhead/node-static#serving-specific-files" rel="nofollow">documentation</a> does not provide this information.</p>
  
  <p>When using <code>serveFile</code> how can I check if the file served does exist? </p>
  
  <pre><code>fileServer.serveFile('/error.html', 500, {}, request, response);
  </code></pre>
  
  <p>In other words, how can I check if the file was served successfully?</p>
  
  <p>Seems that <a href="https://github.com/cloudhead/node-static/blob/b51b8aeffb7cfd1d87d5b730226931a73e84b9a3/lib/node-static.js#L80-L95" rel="nofollow"><code>serveFile</code> function</a> doesn't accept a callback function. Or am I wrong?</p>