var wg sync.WaitGroup
	disks := er.getDisks()
	infos := make([]DiskInfo, len(disks))
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	for _, i := range r.Perm(len(disks)) {
		i := i
		wg.Add(1)
		go func() {
			defer wg.Done()

			disk := disks[i]
			if disk == nil {
				infos[i].Error = errDiskNotFound.Error()

		connectionsPerPeer = 1
	}

	errStr := ""
	var wg sync.WaitGroup
	for index := range globalNotificationSys.peerClients {
		if globalNotificationSys.peerClients[index] == nil {
			continue
		}
		go func(index int) {
			for i := 0; i < connectionsPerPeer; i++ {
				wg.Add(1)
				go func() {
					defer wg.Done()
					err := globalNotificationSys.peerClients[index].DevNull(ctx, r)

	dm.refreshInterval = 500 * time.Millisecond
	var wg sync.WaitGroup
	wg.Add(1)

	ctx, cl := context.WithCancel(context.Background())
	cancel := func() {
		cl()
		wg.Done()
	}

	if !dm.GetLock(ctx, cancel, id, source, Options{Timeout: 5 * time.Minute}) {
		t.Fatal("GetLock() should be successful")
	}

	// Wait until context is canceled
	wg.Wait()
	if ctx.Err() == nil {

// synchronization between read() end with write() end.
func WaitPipe() (*PipeReader, *PipeWriter) {
	r, w := io.Pipe()
	var wg sync.WaitGroup
	wg.Add(1)
	return &PipeReader{
			PipeReader: r,
			wait:       wg.Wait,
		}, &PipeWriter{
			PipeWriter: w,
			done:       wg.Done,
		}

	combined := Mask(atomic.LoadUint64(&ps.types))
	combined.Merge(Mask(mask.Mask()))
	atomic.StoreUint64(&ps.types, uint64(combined))
	if wg != nil {
		wg.Add(1)
	}
	go func() {
		defer func() {
			if wg != nil {
				wg.Done()
			}
			// Clean up and de-register the subscriber
			ps.Lock()
			defer ps.Unlock()
			var remainTypes Mask
			for i, s := range ps.subs {

		LastPing:           time.Now().Unix(),
		BaseFlags:          c.baseFlags,
		clientPingInterval: c.clientPingInterval,
	}
	// Acknowledge Mux created.
	// Send async.
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		var ack message
		ack.Op = OpAckMux
		ack.Flags = m.BaseFlags
		ack.MuxID = m.ID
		m.send(ack)
		if debugPrint {
			fmt.Println("connected stream mux:", ack.MuxID)

		}

		header, err := tarReader.Next()
		switch {

		// if no more files are found return
		case err == io.EOF:
			wg.Wait()
			return asyncErr

		// return any other error
		case err != nil:
			wg.Wait()
			extra := ""
			if n > 0 {
				extra = fmt.Sprintf(" after %d successful object(s)", n)
			}
			return fmt.Errorf("tar file error: %w%s", err, extra)

	sqlDB.SetMaxOpenConns(1)

	tx = tx.Session(&gorm.Session{PrepareStmt: true})

	wg := sync.WaitGroup{}
	for i := 0; i < 100; i++ {
		wg.Add(1)
		go func() {
			user := User{Name: "jinzhu"}
			tx.Create(&user)

			var result User
			tx.First(&result)
			wg.Done()
		}()
	}
	wg.Wait()

	conn, ok := tx.ConnPool.(*gorm.PreparedStmtDB)
	AssertEqual(t, ok, true)

		}(client)
	}

	wg.Add(1)
	go func() {
		defer wg.Done()
		select {
		case <-ctx.Done():
		case ch <- driveSpeedTest(ctx, opts):
		}
	}()

	go func(wg *sync.WaitGroup, ch chan madmin.DriveSpeedTestResult) {
		wg.Wait()
		xioutil.SafeClose(ch)
	}(&wg, ch)

	return ch
}

	}
	defer l.Close()
	serverAddr := l.Addr().String()

	tcpListener, ok := l.(*net.TCPListener)
	if !ok {
		t.Fatalf("failed to assert to net.TCPListener")
	}

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()

		tcpConn, terr := tcpListener.AcceptTCP()
		if terr != nil {
			t.Errorf("failed to accept new connection. %v", terr)
			return
		}
		deadlineconn := New(tcpConn)