code: func (ip *Checker) IsAuthorized(addr string) error {
  	var invalidMatches []string
  
  	host, _, err := net.SplitHostPort(addr)
  	if err != nil {
  		host = addr
  	}
  
  	ok, err := ip.Contains(host)
  	if err != nil {
  		return err
  	}
  
  	if !ok {
  		invalidMatches = append(invalidMatches, addr)
  		return fmt.Errorf("%q matched none of the trusted IPs", strings.Join(invalidMatches, ", "))
  	}
  
  	return nil
  }
docs: // IsAuthorized checks if provided request is authorized by the trusted IPs