code: func tlsDialScan(addr, hostname string) (grade Grade, output Output, err error) {
  	var conn *tls.Conn
  	config := defaultTLSConfig(hostname)
  
  	if conn, err = tls.DialWithDialer(Dialer, Network, addr, config); err != nil {
  		return
  	}
  	conn.Close()
  
  	config.InsecureSkipVerify = false
  	if conn, err = tls.DialWithDialer(Dialer, Network, addr, config); err != nil {
  		grade = Warning
  		return
  	}
  	conn.Close()
  
  	grade = Good
  	return
  }
docs: // tlsDialScan tests that the host can perform a TLS Handshake
  // and warns if the server's certificate can't be verified.