adding futures

daggy/src/ThreadPool.cpp

@@ -3,6 +3,8 @@
 using namespace daggy;
 
 ThreadPool::ThreadPool(size_t nWorkers) {
+  shutdown_ = false;
+  std::lock_guard<std::mutex> lk(guard_);
   for (size_t i = 0; i < nWorkers; ++i) {
     workers_.emplace_back([&]() {
         while (true) {
@@ -36,9 +38,11 @@ void ThreadPool::shutdown() {
 }
 
 std::future<void> ThreadPool::addTask(std::function<void()> fn) {
+  std::packaged_task<void()> task(fn);
+  std::future<void> result = task.get_future();
   {
     std::unique_lock<std::mutex> lk(guard_);
-    taskQueue_.push_back(fn);
+    taskQueue_.push_back(std::move(task));
   }
   cv_.notify_one();
 }