Method pop

async_simple/coro/test/ConditionVariableTest.cpp:263–268

            cv.notifyOne();
        }
        Lazy<> pop(int& i) {
            std::unique_lock lk(mutex);
            co_await cv.wait(mutex, [&]() { return !q.empty(); });
            i = q.front();
            q.pop();
        }
        std::queue<int> q;
        SpinLock mutex;
        ConditionVariable<SpinLock> cv;