code: func (s *DistinctNetSet) Add(ip net.IP) bool {
  	key := s.key(ip)
  	n := s.members[string(key)]
  	if n < s.Limit {
  		s.members[string(key)] = n + 1
  		return true
  	}
  	return false
  }
docs: // Add adds an IP address to the set. It returns false (and doesn't add the IP) if the
  // number of existing IPs in the defined range exceeds the limit.