code: func (s *Store) LeaderID() (string, error) {
  	addr := s.LeaderAddr()
  	configFuture := s.raft.GetConfiguration()
  	if err := configFuture.Error(); err != nil {
  		s.logger.Printf("failed to get raft configuration: %v", err)
  		return "", err
  	}
  
  	for _, srv := range configFuture.Configuration().Servers {
  		if srv.Address == raft.ServerAddress(addr) {
  			return string(srv.ID), nil
  		}
  	}
  	return "", nil
  }
docs: // LeaderID returns the node ID of the Raft leader. Returns a
  // blank string if there is no leader, or an error.