Method await_suspend

test/coroutine/test_task.cpp:61–65

    return false;
  }
  ::std::coroutine_handle<> await_suspend(
      ::std::coroutine_handle<> awaiter) noexcept {
    handle.promise().awaiter = awaiter;
    return handle;
  }
  inline T await_resume() noexcept {
    return ::std::move(handle.promise().value);
  }