C++ Timer - Start & Stop works, Restart doesn't

Question

I am having a trouble exiting a thread using a Restart function. When calling Stop it exits the thread, but Restart which calls Stop and then Start right after - doesn't exit the thread -> calls Start and creates a new thread.

Thanks. Any help would be really helpful and appreciated.

Dummy code to show the problem:

#include <iostream>
#include <thread>
#include <condition_variable>
#include <chrono>

using namespace std;

bool running = false;

unsigned int interval = 5000;

condition_variable cv_work;
mutex mu_cv_work;

void Start()
{
    unique_lock<std::mutex> lock(mu_cv_work);
    running = true;
    lock.unlock();
    thread([]{
        cout << "new thread" << '\n';
        while (running)
        {
            cout << "work..." << '\n';
            unique_lock<std::mutex> lock(mu_cv_work);
            cout << "sleep" << '\n';
            if (cv_work.wait_for(lock, chrono::milliseconds(interval), []{return running == false;}))
            {
                cout << "exit thread" << '\n';
                return;
            }
            cout << "done sleeping" << '\n';
        }
    }).detach();
}

void Stop()
{
    unique_lock<std::mutex> lock(mu_cv_work);
    running = false;
    lock.unlock();
    cv_work.notify_one();
}

void Restart()
{
    Stop();
    Start();
}

int main()
{
    Start();
    cout << "press to Stop" << '\n';
    cin.get();
    Stop();                             // Stop actually exits the Thread
    cout << "press to Start" << '\n';
    cin.get();
    Start();
    cout << "press to Restart" << '\n';
    cin.get();
    Restart();                         // Stop doesn't exit the Thread (Restart calls Stop() and Start())

    return 0;
}

Output:

press to Stop
new thread
work...
sleep
                      // KEY PRESS
exit thread
press to Start
                      // KEY PRESS
new thread
work...
sleep
press to Restart
                      // KEY PRESS
new thread
work...
sleep
done sleeping
work...
sleep

Expected output:

press to Stop
new thread
work...
sleep
                      // KEY PRESS
exit thread    
press to Start
                      // KEY PRESS
new thread
work...
sleep    
press to Restart
                      // KEY PRESS    
exit thread             // THIS LINE
new thread
work...
sleep
done sleeping
work...
sleep