C++11 async

#include "iostream"
#include "future"
#include "chrono"

using namespace std;

bool isPrime(int x)
{
    for(int i = 2; i < x;i++)
    {
        if(x % i == 0)
        {
            return false;
        }
    }

    return true;
}

int do_get_value()
{
    return 10;
}

int main()
{
    //444444443
    int value  = 194232491;
    std::future<bool> fut  = std::async(isPrime,value);
    cout << "please wait....." <<endl;

    std::chrono::milliseconds span(100);
    //while(fut.wait_for(span) == std::future_status::timeout)
    //{
     //   cout<< "has waited 100ms ,timeout." <<endl;
    //}

    fut.wait();
    bool x = fut.get();

    cout << value << (x?" is " : " is not ") <<" prime ."<<endl;
    getchar();
    return 0;
}

int main1()
{
    std::future<int> fut = std::async(do_get_value);
    std::shared_future<int> shFut = fut.share();

    cout << " value is " << shFut.get() <<endl; 
    cout << " value is " << shFut.get()*2 <<endl; 
}