return listen("tcp6", "[::1]:0")
		}
	case "unix", "unixpacket":
		return listen(network, testUnixAddr(t))
	}

	t.Helper()
	t.Fatalf("%s is not supported", network)
	return nil
}

func newDualStackListener() (lns []*TCPListener, err error) {
	var args = []struct {
		network string
		TCPAddr
	}{
		{"tcp4", TCPAddr{IP: IPv4(127, 0, 0, 1)}},
		{"tcp6", TCPAddr{IP: IPv6loopback}},
	}
	for i := 0; i < 64; i++ {

			continue
		}

		if !supportsIPv4map() && differentWildcardAddr(tt.address1, tt.address2) {
			tt.xerr = nil
		}
		var firstErr, secondErr error
		for i := 0; i < 5; i++ {
			lns, err := newDualStackListener()
			if err != nil {
				t.Fatal(err)
			}
			port := lns[0].port()
			for _, ln := range lns {
				ln.Close()
			}
			var ln1 Listener