rsa.go
func (rs *RSASigner) Encode(obj interface{}) ([]byte, error) {
	return rs.alg.Encode(rs, obj)
}
func (rs *RSASigner) Encode(obj interface{}) ([]byte, error) {
	return rs.alg.Encode(rs, obj)
}
// Encode serializes the JSON marshalable obj data as a JWT.