http.Get("https://golang.org/")
net.Dial("tcp", "golang.org:80")
net.Dial("udp", "golang.org:443")

func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {
        ...
	addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", network, address, d.LocalAddr)
        ...
}

func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {
         ...
	networkForResolve := network
	switch network {
	case "tcp", "udp":
		if !supportsIPv6() {
			networkForResolve = network + "4"
		}
	}
	addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", networkForResolve, address, d.LocalAddr)
        ...
}