auth/jwt.go
func Issuer(issuer string) TokenOpt {
	return TokenOpt{func(o *options) {
		o.issuer = issuer
	}}
}
func Issuer(issuer string) TokenOpt {
	return TokenOpt{func(o *options) {
		o.issuer = issuer
	}}
}
// Issuer sets the issuer in the standart claims object.