Save task references (#475)

* Save a tast reference

Important: Save a reference of the created task,
to avoid a task disappearing mid-execution. The
event loop only keeps weak references to tasks.
A task that isn’t referenced elsewhere may get
garbage collected at any time, even before it’s
done. For reliable “fire-and-forget” background
tasks, gather them in a collection

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [unreleased]
 
+- save task references, to avoid a task disappearing mid-execution
 - catch socket.gaierror exception and log this with info level
 - Update dependency coverage to v7.9.2
 - add-on: bump base-image to version 18.0.3