code: func tcpDialScan(addr, hostname string) (grade Grade, output Output, err error) {
  	conn, err := Dialer.Dial(Network, addr)
  	if err != nil {
  		return
  	}
  	conn.Close()
  	grade = Good
  	return
  }
docs: // tcpDialScan tests that the host can be connected to through TCP.