code: func (s *SecretEnvelope) InternalEndpoint() string {
  	secret := &Secret{}
  	if err := proto.Unmarshal(s.Payload, secret); err != nil {
  		return ""
  	}
  	return secret.GetInternalEndpoint()
  }
docs: // InternalEndpoint returns the internal endpoint
  // in the secret envelope, or an empty string
  // if a failure occurs.