Go library for generates/verifies HMAC-based authentication tokens

 This library takes a user-provided *message* (an arbitrary sequence of
 bytes), a *key* (256 bits), and the current time, and produces a
 *token*, which contains the message in a form that can't be read
 or altered without the key.
 .
 This package is compatible with the other implementations at
 https://github.com/fernet. They can exchange tokens freely among
 each other.