#include <iostream>
#include <future>
#include <thread>
#include <chrono>
using namespace std::chrono_literals;
int main()
{
std::shared_future<int> future = std::async(std::launch::async, [](){
std::this_thread::sleep_for(3s);
return 8;
});
std::cout << "waiting...\n";
std::future_status status;
do {
switch(status = future.wait_for(1s); status) {
case std::future_status::deferred: std::cout << "deferred\n"; break;
case std::future_status::timeout: std::cout << "timeout\n"; break;
case std::future_status::ready: std::cout << "ready!\n"; break;
}
} while (status != std::future_status::ready);
std::cout << "result is " << future.get() << '\n';
}