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