How do I notify a c++ future without setting a value?

I have a thread waiting on a future. In the event where my application is shut down, I would like to join the thread. How do I go about notifying the future without fudging it and setting it to some value?

auto promise = std::promise<std::string>();
...
auto future = promise.get_future();
auto consumer = std::thread([&]
{
   while (future.wait_for(10ms)){
       // do something
       std::cout << future.get().c_str();
   }
});
...
consumer.join();