title: Coroutines the proper way to add a job as child of another?
body: <p>Given we have <code>job1 : Job</code> and <code>job2 : Job</code> and we want to make <code>job2</code> a child of <code>job1</code> (they where created separately have no relation).</p>
  
  <p>What is the correct way to declare that relationship? so that when <code>job1</code> is cancelled <code>job2</code> is cancelled as well...</p>
  
  <p>I tried <code>job1.attachChild(e1.job2 as ChildJob)</code> but this is internal api.
  I do not want to do some hack when i launch job2 from job1 coroutine.</p>