net.DialTCPnet.TCPConnDialTCP
func connectAddress(addr *net.TCPAddr, wg *sync.WaitGroup) error {
    start := time.Now()
    conn, err := net.DialTCP("tcp", nil, addr)
    if err != nil {
        log.Printf("Dial failed for address: %s, err: %s", addr.String(), err.Error())
        return err
    }
    elasped := time.Since(start)
    log.Printf("Connected to address: %s in %dms", addr.String(), elasped.Nanoseconds()/1000000)
    conn.Close()
    wg.Done()
    return nil
}