title: Why passing in Async functions to Node.js Express.js router?
body: <p>I try learning node.js and express for developing a web app. Today I have read a post about <a href="https://stackoverflow.com/questions/44813401/passing-in-async-functions-to-node-js-express-js-router">"Passing in Async functions to Node.js Express.js router"</a>.</p>
  
  <p>This question doesn't fit into my mental model how route handling works.</p>
  
  <p>I was assuming, that in</p>
  
  <pre><code>app.Method('path', function);
  </code></pre>
  
  <p>e.q.</p>
  
  <pre><code>app.post('/lgn', (req, resp) =&gt; {...})
  </code></pre>
  
  <p>the function would be the callback. And I thought, that async functions are the modern way of callbacks.</p>
  
  <p>Why should it be neccessary to define an async callback?</p>