Terminating thread on DLL unload

I'm trying to write a DLL plug-in for a third-party software.In the plug in i'm creating a thread in an initialization function which is called by the hosting program. However, there is no shutdown routine in which I could properly terminate the thread. I'm tried this code:

DLL_EXPORT void InitFunction() // is called by the host application
{
    myThread = std::move(std::thread{myThreadFunction});
}
bool WINAPI DllMain( HINSTANCE hDll, DWORD fdwReason, LPVOID lpvReserved )
{
    switch (fdwReason)
    {
    case DLL_PROCESS_ATTACH:
    {
        DisableThreadLibraryCalls(hDll);
    }   break;
    case DLL_PROCESS_DETACH:
    {
        if(myThread.joinable())
            myThread.join();
    }break;
    case DLL_THREAD_ATTACH:
        break;
    case DLL_THREAD_DETACH:
        break;
    }
    return true;
}

I know this won't worl because windows would call DllMain upon thread termintation, but the DllMain is still running and therefore would deadlock. I tried using DisableThreadLibraryCalls() in different places in the Dll, but that didn't work either. So, How can I terminate the threads in my DLL properly?