C++11 multithreaded projects examples

Trying to understand how to write a multithreaded program using features of 11 or 14 standard. I've got enough simple examples with using std::async or std::thread, but i can't find any good architecture example. Does anyone know an opensource multithreaded project where i can take a look to know how multithreading works in real life? Not abstract examples with simple classes and functions like doSomething().