code: func (b *Backend) lockGroupMeta(groupMeta *tasks.GroupMeta) error {
  	groupMeta.Lock = true
  	encoded, err := json.Marshal(groupMeta)
  	if err != nil {
  		return err
  	}
  
  	return b.getClient().Set(&gomemcache.Item{
  		Key:        groupMeta.GroupUUID,
  		Value:      encoded,
  		Expiration: b.getExpirationTimestamp(),
  	})
  }
docs: // lockGroupMeta acquires lock on group meta data