You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: sockopt_test.go
    path of file: ./repos/bytom/lib/golang.org/x/net/ipv6
    
    the code of the file until where you have to start completion: // Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ipv6_test

import (
	"fmt"
	"net"
	"runtime"
	"testing"

	"golang.org/x/net/internal/
    
func TestConnResponderPathMTU(t *testing.T) {
	switch runtime.GOOS {
	case "nacl", "plan9", "windows":
		t.Skipf("not supported on %s", runtime.GOOS)
	}
	if !supportsIPv6 {
		t.Skip("ipv6 is not supported")
	}

	ln, err := net.Listen("tcp6", "[::1]:0")
	if err != nil {
		t.Fatal(err)
	}
	defer ln.Close()

	done := make(chan bool)
	go connector(t, "tcp6", ln.Addr().String(), done)

	c, err := ln.Accept()
	if err != nil {
		t.Fatal(err)
	}
	defer c.Close()

	if pmtu, err := ipv6.NewConn(c).PathMTU(); err != nil {
		switch runtime.GOOS {
		case "darwin": // older darwin kernels don't support IPV6_PATHMTU option
			t.Logf("not supported on %s", runtime.GOOS)
		default:
			t.Fatal(err)
		}
	} else {
		t.Logf("path mtu for %v: %v", c.RemoteAddr(), pmtu)
	}

	<-done
}