Long story short

In the docs there is an explanation on how to create a Background task (in this case, a Redis listener)

https://docs.aiohttp.org/en/stable/web_advanced.html

I want to create a background task to listen for Postgres notifications.

Expected behaviour

In the docs, the example is app.loop.create_task(listen_to_redis(app)) and this should be the official working example or a different one if this one is deprecated.

Actual behaviour

When running the code, a warning occurs:

gateway.py:39: DeprecationWarning: loop property is deprecated app['listener'] = app.loop.create_task(listen(app)) Traceback (most recent call last): File "gateway.py", line 117, in <module> web.run_app(app) File "/home/goc/.virtualenvs/doorway/lib/python3.7/site-packages/aiohttp/web.py", line 210, in run_app reuse_port=reuse_port)) File "/usr/local/lib/python3.7/asyncio/base_events.py", line 573, in run_until_complete return future.result() concurrent.futures._base.CancelledError

Steps to reproduce

https://github.com/gcetusic/doorway/blob/master/gateway.py#L39

Your environment

Aiohttp server instance (version 3.5.3), Ubuntu 18.04