TLDR: Is there a way to use the call_later function within a worker task? 
(Or am I just looking at this issue the wrong way?)

Software - Python 3.6, Django 2.0.2, Channels 2.0.2, trying to run this on 
either / both Windows 10 and Ubuntu 17.10 if it matters

Longer version - I'm having surprisingly few problems with wrapping my head 
around the new Channels 2, especially since this is the first I've been 
using asyncio and it's been about 10 years since I've used Twisted. All my 
personal sample code that I've been trying to write has been working great.

Except... I have the situation where I want to schedule an event for some 
fixed period of time in the future - say 30 seconds.
But, it's also necessary for me to be able to cancel that scheduled event.

I've tried a number of different combinations for the worker task between 
SyncConsumer and AsyncConsumer, and different combinations of async and 
regular methods, and get a variety of different errors. But the bottom line 
is that I haven't stumbled across the magic sauce that will let this work.

I _can_ get the delay to work by using the asyncio.sleep method, using the 
pattern shown in the "Delay server" paragraph in the "What's new in 
Channels 2?" section of the docs. But while that method (sleep) returns a 
generator object, I don't see where that does me any good with trying to 
cancel that sleep.

I know I can make this work by setting some variable, and check that after 
the sleep has finished to determine whether or not I still need to do my 
work, but that just "feels wrong" to me for some reason.

Is there something simple that I'm missing? Or does this fit into the 
category of "Don't do that!"


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