std::async 使用中遇到后面代码执行不到问题

std::async(std::launch::async, []() {
	while (true)
	{
		std::this_thread::sleep_for(std::chrono::seconds(3));
		std::cout << 867 << std::endl;
	}
	return 8;
	//return 8;
});
std::cout << "hello" << std::endl;
//按上面的写法后面的输出语句不会被执行到

std::future<int> f = std::async(std::launch::async, []() {
	while (true)
	{
		std::this_thread::sleep_for(std::chrono::seconds(3));
		std::cout << 8 << std::endl;
	}
	return 8;
	//return 8;
});

std::cout << "hello" << std::endl;
//按上面的写法后面的输出语句才会被执行到