code: func (cgi *ConsumergroupInstance) RegisterWithSubscription(subscriptionJSON []byte) error {
  	node := fmt.Sprintf("%s/consumers/%s/ids/%s", cgi.cg.kz.conf.Chroot, cgi.cg.Name, cgi.ID)
  	err := cgi.cg.kz.create(node, subscriptionJSON, true)
  	if err == zk.ErrNodeExists {
  		return ErrInstanceAlreadyRegistered
  	}
  	return err
  }
docs: // RegisterSubscription registers the consumer instance in Zookeeper, with its subscription.