Auth token renewal

[vincentgiraud]

Is your feature request related to a problem? Please describe.
Once the oauth token expired, an "unauthenticated" grpc exception will be raised: "Failed to parse bearer token, see cause for details"

Describe the solution you'd like
I'd like a coroutine (or else) to renew the token with or without recreating the channel hence the worker.

Describe alternatives you've considered
Catching the exception and calling again the main function

[dimastbk]

For inspiration: https://github.com/googleapis/google-auth-library-python/blob/32ed6015ea71f9dd1a594b3caa88fd328f56b0b7/google/auth/transport/grpc.py#L37