title: Flutter: Wait for async void method
body: <p>I have an async save method that writes to the file system. The return type is void. I want to update the ui as soon as save is finished. Usually I would do that with the then() method, but it's not applicable with a return type of void? So how can I get notified, when save has finished?</p>
  
  <pre><code>  void save(Folder folder) async {  
     .....
    }
  </code></pre>