split.py example fails with InvalidStateError

[iangoldby]

1. Create a new Python 3.9 environment.
2. pip install aioreactive
3. Download and run split.py from examples/streams Expected result: see values being printed out. Actual result:

   Exception in callback MailboxProcessor.__process_events()
   handle: <Handle MailboxProcessor.__process_events()>
   Traceback (most recent call last):
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\asyncio\events.py", line 80, in _run
   self._context.run(self._callback, *self._args)
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\site-packages\expression\core\mailbox.py", line 152, in __process_events
   cont(msg)
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\site-packages\expression\core\aiotools.py", line 45, in done
   future.set_result(value)
   asyncio.exceptions.InvalidStateError: invalid state
   Exception in callback MailboxProcessor.__process_events()
   handle: <Handle MailboxProcessor.__process_events()>
   Traceback (most recent call last):
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\asyncio\events.py", line 80, in _run
   self._context.run(self._callback, *self._args)
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\site-packages\expression\core\mailbox.py", line 152, in __process_events
   cont(msg)
   File "C:\Users\Ian\.conda\envs\aioreactive\lib\site-packages\expression\core\aiotools.py", line 45, in done
   future.set_result(value)
   asyncio.exceptions.InvalidStateError: invalid state

[davidia]

The asyncio event loop is closing immediately and cancelling the futures that do the work resulting in this error. If you stick

await asyncio.sleep(5)

at the end of the main function the error goes away.