code: func (s *Sentinel) putToTop(addr string) {
  	addrs := s.Addrs
  	if addrs[0] == addr {
  		// Already on top.
  		return
  	}
  	newAddrs := []string{addr}
  	for _, a := range addrs {
  		if a == addr {
  			continue
  		}
  		newAddrs = append(newAddrs, a)
  	}
  	s.Addrs = newAddrs
  }
docs: // putToTop puts Sentinel address to the top of address list - this means
  // that all next requests will use Sentinel on this address first.
  //
  // From Sentinel guidelines:
  //
  // The first Sentinel replying to the client request should be put at the
  // start of the list, so that at the next reconnection, we'll try first
  // the Sentinel that was reachable in the previous connection attempt,
  // minimizing latency.
  //
  // Lock must be held by caller.