Method enqueue

dependencies/httplib/httplib.h:546–550

  ~ThreadPool() override = default;

  void enqueue(std::function<void()> fn) override {
    std::unique_lock<std::mutex> lock(mutex_);
    jobs_.push_back(std::move(fn));
    cond_.notify_one();
  }

  void shutdown() override {
    // Stop all worker threads...