title: How to stop the preview server
body: <p>This code is based on wintersmith static site generator</p>
  
  <p>In my code I'm starting the preview server like this:</p>
  
  <pre><code>env.preview(function(error, server) {
    if (error) throw error;
    console.log('Server running!');
    setTimeout(function(){
      console.log("going to shut it down")
      server.stop();
    }, 3000)
  });
  </code></pre>
  
  <p>This is taken from the example. I would expect the preview server to stop after 3 seconds, but instead I get an error, that server is undefined.</p>
  
  <p>I looked a bit closer at it and indeed: server is undefined. Anything I'm doing wrong? How am I able to stop the preview server?</p>