// Pretend we didn't and put the tokens back.
			s.cur -= n
			s.notifyWaiters()
		default:
			isFront := s.waiters.Front() == elem
			s.waiters.Remove(elem)
			// If we're at the front and there're extra tokens left, notify other waiters.
			if isFront && s.size > s.cur {
				s.notifyWaiters()
			}
		}
		s.mu.Unlock()
		return ctx.Err()

	case <-ready: