async_mutex, lock in a task, and unlock in the other task, the assert != not_locked failed?

[bbqz007]

async_mutex mtx;
tsk_lock=
[&](){
 assert(mtx.try_lock());
 co_return;
}

tsk_unlock=
[&](){
 mtx.unlock();  /// failed assert != not_locked
 co_return;
}

when_all(tsk_lock(), tsk_unlock());

[bbqz007]

it is the problem there is some task without co_return;

                   auto tsk_lock = [&]()->cppcoro::task<>{
                        mtx.try_lock();
                        // co_return;       ///  without it, it makes things unexpected. it makes my unlock() in next task failed assert != not_locked
                    };
                    auto tsk_mtx = [&](int i)->cppcoro::task<>{
                        co_await A(i);
                        co_await mtx.lock_async();
                        co_await Aa(i);
                        co_await pool.schedule();
                        co_await C(i);
                        mtx.unlock();
                        co_await D(i);
                        co_return;
                    };
                    auto tsk_unlock = [&]()->cppcoro::task<>{
                        mtx.unlock();
                        // co_return;
                    };
                   cppcoro::when_all(tsk_lock(), tsk_mtx(1), tsk_mtx(2), tsk_mtx(3), tsk_unlock());