code: func (l *LoadBalancer) RemoveBackend(b NetAddr) {
  	l.Lock()
  	defer l.Unlock()
  	l.currentIndex = -1
  	for i := range l.backends {
  		if l.backends[i].Equals(b) {
  			l.backends = append(l.backends[:i], l.backends[i+1:]...)
  			l.dropConnections(b)
  			return
  		}
  	}
  }
docs: // RemoveBackend removes backend