In line
https://github.com/square/go-jose/blob/643bdf8caec0de8a54ec3e8f8601d57992f35510/jwk.go#L112
if key is nil error message is
'square/go-jose: unknown key type '%!s()''
If change this line to
'return nil, fmt.Errorf("square/go-jose: unknown key type '%T'", key)'
then everything is OK. Message will be
'square/go-jose: unknown key type '''
From fmt package docs:
'%T a

Token from User Credentials.

This method should be used when you just registered a user and any other special cases.

I think this should be "This method should be used when you want to authenticate a user and any other special cases." because the function

public function tokenFromCredentials(Guard $auth, Request $request)
{
    // get some credentials
    $credential

This behaviour is encoded in an internal flatten serializer.