hostTests: []nssHostTest{{"google.com", "myhostname", hostLookupCgo}},
		},
		// Issue 24393: make sure "Resolver.PreferGo = true" acts like netgo.
		{
			name:     "resolver-prefergo",
			resolver: &Resolver{PreferGo: true},
			c: &conf{
				preferCgo: true,
				netCgo:    true,
			},
			resolv: defaultResolvConf,
			nss:    nssStr(t, ""),
			hostTests: []nssHostTest{

					Response: true,
					RCode:    dnsmessage.RCodeSuccess,
				},
				Questions: q.Questions,
			}
			if n == "udp" {
				r.Header.Truncated = true
			}
			return r, nil
		},
	}
	r := Resolver{PreferGo: true, Dial: fake.DialContext}
	for _, tt := range dnsTransportFallbackTests {
		ctx, cancel := context.WithCancel(context.Background())
		defer cancel()

//
// Adding netdns=go to GODEBUG will prefer the go resolver.
// Adding netdns=cgo to GODEBUG will prefer the cgo resolver.
//
// The Resolver struct has a PreferGo field that user code
// may set to prefer the go resolver. It is documented as being
// equivalent to adding netdns=go to GODEBUG.
//
// When deciding which resolver to use, we first check the PreferGo field.
// If that is not set, we check the GODEBUG setting.

		out.Resolver = newResolver(common.ConnectionTimeout, "", "")
	}
	return out
}

func newResolver(timeout time.Duration, protocol, dnsServer string) *net.Resolver {
	return &net.Resolver{
		PreferGo: true,
		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
			d := net.Dialer{
				Timeout: timeout,
			}
			nt := protocol
			if nt == "" {
				nt = network
			}

		t.Skip("skipping on plan9")
	}
	rDeadlineExcceeded := &Resolver{PreferGo: true, Dial: func(ctx context.Context, network, address string) (Conn, error) {
		return nil, context.DeadlineExceeded
	}}
	rCancelled := &Resolver{PreferGo: true, Dial: func(ctx context.Context, network, address string) (Conn, error) {
		return nil, context.Canceled
	}}

// A Resolver looks up names and numbers.
//
// A nil *Resolver is equivalent to a zero Resolver.
type Resolver struct {
	// PreferGo controls whether Go's built-in DNS resolver is preferred
	// on platforms where it's available. It is equivalent to setting
	// GODEBUG=netdns=go, but scoped to just this resolver.
	PreferGo bool

	// StrictErrors controls the behavior of temporary errors

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"reflect"
	"slices"
	"testing"
	"time"

	"golang.org/x/net/dns/dnsmessage"
)

func TestResolverDialFunc(t *testing.T) {
	r := &Resolver{
		PreferGo: true,
		Dial: newResolverDialFunc(&resolverDialHandler{
			StartDial: func(network, address string) error {
				t.Logf("StartDial(%q, %q) ...", network, address)
				return nil
			},

			var name string
			if def {
				name = "default/"
			} else {
				name = "go/"
			}
			t.Run(name+server, func(t *testing.T) {
				t.Parallel()
				r := DefaultResolver
				if !def {
					r = &Resolver{PreferGo: true}
				}
				fn(t, r, server)
			})
		}
	}
}

func TestNSLookupMX(t *testing.T) {
	testenv.MustHaveExternalNetwork(t)

	testLookup(t, func(t *testing.T, r *Resolver, server string) {

pkg net, method (*UnixListener) SetUnlinkOnClose(bool)
pkg net, type Buffers [][]uint8
pkg net, type Dialer struct, Resolver *Resolver
pkg net, type Resolver struct
pkg net, type Resolver struct, PreferGo bool
pkg net/url, func PathEscape(string) string
pkg net/url, func PathUnescape(string) (string, error)
pkg net/url, method (*URL) Hostname() string
pkg net/url, method (*URL) MarshalBinary() ([]uint8, error)

        and:
        sort([prefer30, prefer10, prefer20, require20, require30]) == [require30, require20, prefer30, prefer20, prefer10]

        and:
        sort([prefer30, dynamic1, prefer10]) == [prefer30, prefer10, dynamic1]

        and:
        sort([dynamic1, prefer10, fromLock, dynamic2]) == [fromLock, prefer10, dynamic1, dynamic2]

        and: