Access token might be inconsistent across threads

[Niccari]

In v2.0.x, access tokens are issued per thread. However, credentials are shared. This can lead to inconsistencies in access tokens between threads. Specific issues that can occur are as follows:

• Token refreshes occur as many times as the number of threads.
• Credentials are shared, so when multiple threads simultaneously refresh or read a token, it may become outdated.