Bump Go version to indicate correct minimum requirement (#452)

* Bump Go version to indicate correct minimum requirement

The minimum requirement that we have was silently bumped to 1.21 in #441 because of the `slices` package. It seems that we did not update the `go.mod` when we updated our CI range, because CI did not fail because it was not testing older versions.

We probably should just update the `go.mod` when we update the CI target in the future? Although we could theoretically stay at 1.21 in terms of the code base.

* Removed outdated build tags

* Remove more build tags

* Removed code for Go < 1.20

Fix bug in validation of multiple audiences (#441)

* Fix bug in validation of multiple audiences

In a situation where multiple audiences are validated by the
validator, the order of evaluation of the for-range loop
affects the result.

If we produce matches such as:

```
{
  "example.org": true,
  "example.com": false,
}
```

and we configured the validator to expect a single match on
audience, the code would either:

1. produce "token has invalid audience" if "example.org" was
evaluated first

2. produce a passing result if "example.com" was evaluated first

This commit fixes this bug, and adds a suite of tests as well
as regression tests to prevent this issue in future.

* Adding three more test cases to be sure

* Removing required alltogether form verifyAudience

* Removing required

---------

Co-authored-by: Christian Banse <oxisto@aybaze.com>

Merge commit from fork

* Remove strings.Split and add parseToken function

* review and add tests

Backporting 0951d18 to v4

Merge commit from fork

* Initial draft of adding text to ParseWithClaims

* Adjusted example and referring to the example in Parse functions

* Backporting logic from v5

* Added a test

Release v5.2.1

Release v5.2.0

Release v5.1.0

enable jwt.ParsePublicKeyFromPEM to parse PKCS1 Public Key (#120)

Adjusting the error checking example (#270)

This PR adjusts the error checking example so that a check for an invalid signature is also included.

See discussion in #143