multi-thread print also prints thread id

src/multi_threading_utils.h

@@ -135,7 +135,8 @@ template <typename... Args>
 inline void locked_cout(const CoutColor& color, const Args&... rest)
 {
   std::lock_guard<std::mutex> lock_cout{details::the_infamous_cout_mutex};
-  std::cout << color << details::printTime() << " ";
+  std::cout << color << "[thread " << core::get_thread_id()
+            << "]" << details::printTime() << " ";
 
   details::cout_impl(rest...);
 }