// cases in TestResolveAddr(). Need to wrap IPv6 addresses in square
// brackets.
func determineLocalHostIPString(t *testing.T) string {
	ips, err := net.DefaultResolver.LookupNetIP(context.Background(), "ip", "localhost")
	if err != nil || len(ips) == 0 {
		t.Fatalf("Test setup failure - unable to determine IP of localhost: %v", err)
	}
	var ret string
	for _, ip := range ips {

		// if there are more than one lookup function, ignore all but first
		addrs, lookupErr = lookupIPAddr[0](ctx, host)
	} else {
		addrs, lookupErr = net.DefaultResolver.LookupNetIP(ctx, "ip", host)
	}
	if lookupErr != nil || len(addrs) == 0 {
		return "", fmt.Errorf("lookup failed for IP address: %w", lookupErr)
	}
	var resolvedAddr string

	for _, addr := range addrs {

pkg go/types, type TypeParamList struct
pkg go/types, type Union struct
pkg net, func TCPAddrFromAddrPort(netip.AddrPort) *TCPAddr
pkg net, func UDPAddrFromAddrPort(netip.AddrPort) *UDPAddr
pkg net, method (*Resolver) LookupNetIP(context.Context, string, string) ([]netip.Addr, error)
pkg net, method (*TCPAddr) AddrPort() netip.AddrPort
pkg net, method (*UDPAddr) AddrPort() netip.AddrPort

	for _, addr := range addrs {
		ips = append(ips, addr.(*IPAddr).IP)
	}
	return ips, nil
}

// LookupNetIP looks up host using the local resolver.
// It returns a slice of that host's IP addresses of the type specified by
// network.
// The network must be one of "ip", "ip4" or "ip6".
func (r *Resolver) LookupNetIP(ctx context.Context, network, host string) ([]netip.Addr, error) {

		case "MX":
			_, err := r.LookupMX(context.Background(), req)
			return err
		case "NS":
			_, err := r.LookupNS(context.Background(), req)
			return err
		case "NetIP":
			_, err := r.LookupNetIP(context.Background(), "ip", req)
			return err
		case "SRV":
			const service = "service"
			const proto = "proto"
			req = req[len(service)+len(proto)+4:]

		{"(*Resolver).LookupIP", Method, 15},
		{"(*Resolver).LookupIPAddr", Method, 8},
		{"(*Resolver).LookupMX", Method, 8},
		{"(*Resolver).LookupNS", Method, 8},
		{"(*Resolver).LookupNetIP", Method, 18},
		{"(*Resolver).LookupPort", Method, 8},
		{"(*Resolver).LookupSRV", Method, 8},
		{"(*Resolver).LookupTXT", Method, 8},
		{"(*TCPAddr).AddrPort", Method, 18},
		{"(*TCPAddr).Network", Method, 0},