title: how to set a middleware only for a specific resolver in Graphql backend using Apollo Express?
body: <p>In Rest API, if you want to set a middleware just for a specific route, you can use this for example:</p>
  <pre><code>router
    .route('/top-5-cheap')
    .get(tourControllers.middleAliasApi, tourControllers.getAllTours);
  </code></pre>
  <p>so in this case, middleAliasApi middleware is executed only if the user sends a request to this route.</p>
  <p>How can i do the same in Graphql app?
  For example, execute a middleware only if the user queries a specific resolver.
  I'm using Apollo-express-server in backend.</p>