code: func (s *Server) numPeers() (int, error) {
  	future := s.raft.GetConfiguration()
  	if err := future.Error(); err != nil {
  		return 0, err
  	}
  
  	return autopilot.NumPeers(future.Configuration()), nil
  }
docs: // numPeers is used to check on the number of known peers, including potentially
  // the local node. We count only voters, since others can't actually become
  // leader, so aren't considered peers.