title: How can I `await` on an Rx Observable?
body: <p>I'd like to be able to await on an observable, e.g.</p>
  
  <pre><code>const source = Rx.Observable.create(/* ... */)
  //...
  await source;
  </code></pre>
  
  <p>A naive attempt results in the await resolving immediately and not blocking execution</p>
  
  <p>Edit:
  The pseudocode for my full intended use case is:</p>
  
  <pre><code>if (condition) {
    await observable;
  }
  // a bunch of other code
  </code></pre>
  
  <p>I understand that I can move the other code into another separate function and pass it into the subscribe callback, but I'm hoping to be able to avoid that.</p>