[BUG] ensure_future reference should be saved until task is end

[homm]

https://github.com/dmontagu/fastapi-utils/blob/3ef27a6f67ac10fae6a8b4816549c0c44567a451/fastapi_utils/tasks.py#L78

https://docs.python.org/3/library/asyncio-future.html#asyncio.ensure_future

Save a reference to the result of this function, to avoid a task disappearing mid-execution.

[priyanshu-panwar]

This project seems to be dead now. You can collaborate here : https://github.com/priyanshu-panwar/fastapi-utilities | This is based on the same project. https://pypi.org/project/fastapi-utilities/0.1.0/