#include <iostream>
#include <mutex>
#include <string>
#include <thread> 

std::mutex cout_mutex { };

void task_A()
{
    auto id = std::this_thread::get_id();
    cout_mutex.lock();
    std::cout << "My ID: " << id << std::endl;
    cout_mutex.unlock();
}

void task_B(std::string const& message)
{
    cout_mutex.lock();
    std::cout << message << std::endl;
    cout_mutex.unlock();
}

int main()
{
    std::thread t1 { task_A };
    std::thread t2 { task_B, "A message from t2" };

    cout_mutex.lock();
    std::cout << "Starting!" << std::endl;
    cout_mutex.unlock();

    t1.join();
    t2.join();
}