title: Akka-http: How to get custom header from a request?
body: <p>I send following headers in a request to my akka-http api: <code>"Content-type": "application/json"</code>, <code>"Accept": "application/json"</code>, <code>"AppId": "some_id"</code>.</p>
  
  <p>How do I get "AppId" custom header in my akka-http route?</p>
  
  <pre><code>(get &amp; parameters("id")) { (id) =&gt;
        complete {
          val appId = ?? // I want to get custom header here.
        }
      } 
  </code></pre>
  
  <p>Thanks.</p>