Only minor changes

[xyproto]

• Add a Register method in hmac.go, for less repetition of code
• Remove a few lines of unreachable code in errors.go

All tests pass.

[lggomez]

Hi @xyproto, per #462 this repo has been deprecated and migrated to a new organization: https://github.com/golang-jwt/jwt

As stated in golang-jwt/jwt#7, none if the new maintainers will be copying the original implementations of PRs of interest to respect the authors, but will rather encourage them to migrate to the new repo (and also check if their contribution is still applicable)

• The current default branch is main, respecting the old v3 version of this package: https://github.com/golang-jwt/jwt
• For changes that are break API-compatibility, the v4 branch is recommended (which will be later on merged to main): https://github.com/golang-jwt/jwt/tree/v4

Regards