auth/jwt.go
func Logger(l handler.Logger) TokenOpt {
	return TokenOpt{func(o *options) {
		o.logger = l
	}}
}
func Logger(l handler.Logger) TokenOpt {
	return TokenOpt{func(o *options) {
		o.logger = l
	}}
}
// Logger defines the logger to be used whenever detailed messages have to be
// printed out.