It's crucial to have an analogue of threadlocal object for coroutines. Tools 
like newrelic use it to provide deep performance analysis, web developers need 
to know details about the current request being served etc.

The proposed solution to this problem is to add an API to set a context_id when 
asyncio.Task is created. This context_id will then be automatically assigned to 
all callbacks, futures and tasks the original task has given birth to.