Fixed typo (GH-11522)

Fixed typo (GH-11522)

Given example does not run, loop variable is missing.

Secondly, this is bad example how to handle shutdown signal, because it would cause `RuntimeError: Event loop stopped before Future completed.`

Perhaps it would be better to cancel all tasks instead of closing loop directly?

Did not create issue, because question is quite simple.
(cherry picked from commit ceb842e155f5fa0109fa88d52da3d1f5e73490ad)

Co-authored-by: Alexander Vasin <hi@alvass.in>