code: func (s *Sentinel) Discover() error {
  	addrs, err := s.SentinelAddrs()
  	if err != nil {
  		return err
  	}
  	s.mu.Lock()
  	for _, addr := range addrs {
  		if !stringInSlice(addr, s.Addrs) {
  			s.Addrs = append(s.Addrs, addr)
  		}
  	}
  	s.mu.Unlock()
  	return nil
  }
docs: // Discover allows to update list of known Sentinel addresses. From docs:
  //
  // A client may update its internal list of Sentinel nodes following this procedure:
  // 1) Obtain a list of other Sentinels for this master using the command SENTINEL sentinels <master-name>.
  // 2) Add every ip:port pair not already existing in our list at the end of the list.