if atomic.LoadUint32(&l.done) == 0 {
		if err := f(); err != nil {
			return err
		}
		// Mark as done only when f() is successful
		atomic.StoreUint32(&l.done, 1)
	}
	return nil
}

// DoWithContext is similar to Do except that it accepts a context as an argument to be passed.
func (l *Init) DoWithContext(ctx context.Context, f func(context.Context) error) error {
	if atomic.LoadUint32(&l.done) == 0 {

	if done == nil {
		done = make(chan *Call, 10) // buffered.
	} else {
		// If caller passes done != nil, it must arrange that
		// done has enough buffer for the number of simultaneous
		// RPCs that will be using that channel. If the channel
		// is totally unbuffered, it's best not to run at all.
		if cap(done) == 0 {
			log.Panic("rpc: done channel is unbuffered")
		}
	}
	call.Done = done
	client.send(call)

// are available or ctx is done. On success, returns nil. On failure, returns
// ctx.Err() and leaves the semaphore unchanged.
func (s *Weighted) Acquire(ctx context.Context, n int64) error {
	done := ctx.Done()

	s.mu.Lock()
	select {
	case <-done:
		// ctx becoming done has "happened before" acquiring the semaphore,
		// whether it became done before the call began or while we were

	str("AAAAAAAA", "BBBBBBBBB")
}

func wait(done <-chan struct{}) bool {
	for i := 0; i < 10; i++ {
		runtime.GC()
		select {
		case <-done:
			return true
		default:
		}
	}
	return false
}

func slice() {
	s := make([]byte, 100)
	s[0] = 1
	one := unsafe.SliceData(s)

	done := make(chan struct{})
	runtime.SetFinalizer(one, func(*byte) { close(done) })

	h := g(one)

	if wait(done) {

	// The close of the Done channel may happen asynchronously,
	// after the cancel function returns.
	//
	// WithCancel arranges for Done to be closed when cancel is called;
	// WithDeadline arranges for Done to be closed when the deadline
	// expires; WithTimeout arranges for Done to be closed when the timeout
	// elapses.
	//
	// Done is provided for use in select statements:
	//

	s []int
}

func TestSlice(t *testing.T) {
	done := make(chan struct{})
	a := make([]int, N+10)

	x := &X{a}

	go func() {
		for i := 0; i < N; i++ {
			x.s = x.s[1:9]
		}
		done <- struct{}{}
	}()
	go func() {
		for i := 0; i < N; i++ {
			x.s = x.s[0:8] // should only write len
		}
		done <- struct{}{}
	}()
	<-done
	<-done

	if cap(x.s) != cap(a)-N {

	// This is why the slow path falls back to a mutex, and why
	// the o.done.Store must be delayed until after f returns.

	if o.done.Load() == 0 {
		// Outlined slow-path to allow inlining of the fast-path.
		o.doSlow(f)
	}
}

func (o *Once) doSlow(f func()) {
	o.m.Lock()
	defer o.m.Unlock()
	if o.done.Load() == 0 {
		defer o.done.Store(1)
		f()
	}

	// are finished using the waitgroup
	n2DoneWG := sync.WaitGroup{}

	startCh, blockedCh := make(chan struct{}), make(chan struct{})
	n1DoneWG.Add(n1)
	for i := 0; i < n1; i++ {
		go func() {
			defer n1DoneWG.Done()
			<-startCh

			target.Add(1)
			// let's finish using the waitgroup immediately
			target.Done()
		}()
	}

	n2BeforeWaitWG.Add(n2)
	n2DoneWG.Add(n2)
	for i := 0; i < n2; i++ {
		go func() {

		for {
			_, ok := <-c
			if !ok {
				done <- true
				return
			}
			x++
		}
	}()
	for i := 0; i < 10; x++ {
		i++
		c <- true
	}
	close(c)
	<-done
}

func TestNoRaceForIncr(t *testing.T) {
	done := make(chan bool)
	x := 0
	go func() {
		x++
		done <- true
	}()
	for i := 0; i < 0; x++ {
	}
	<-done
}

func TestRacePlus(t *testing.T) {

			}
			err = next(resp.Msg)
			if err != nil {
				s.cancel(err)
				return err
			}
		}
	}
}

// Done will return a channel that will be closed when the stream is done.
// This mirrors context.Done().
func (s *Stream) Done() <-chan struct{} {
	return s.ctx.Done()
}

// Err will return the error that caused the stream to end.
// This mirrors context.Err().
func (s *Stream) Err() error {