title: How to stop asyncio loop with multiple tasks
body: <p>I can't figure how to stop loop after one task is finished. In sample when WsServe count to 5 I expect loop to close. But instead stop I got <em><strong>RuntimeError: Cannot close a running event loop</strong></em></p>
  <pre><code>#!/usr/bin/env python
  import asyncio
  
  async def rxer():
      i=0
      while True:
          i+=1
          print ('Rxer ',i)
          await asyncio.sleep(1)
  
  async def WsServe():
      for i in range(5):
          print ('WsServe',i)
          await asyncio.sleep(1)
  
      print ('Finish')
      loop.stop()
      loop.close()
  
  loop=asyncio.get_event_loop()
  loop.create_task(rxer())
  loop.run_until_complete(WsServe())
  loop.run_forever()
  </code></pre>