Consider using ContextVar instead of threading.local

[eliasdorneles]

A ContextVar behaves the same as threading.local in multi-threading environments, but it will also work for coroutines as well.

Consider using that to make your library compatible with async contexts.

[jamesmishra]

Sorry for the late reply. You are correct that a ContextVar would be the far superior design.

If I have the time, I will try to make the change, but if you want to submit the PR, I would be happy to merge it.