avoid read before write

lab6/pipe_tester.cpp

@@ -21,8 +21,8 @@ void reader() {
 
 int main() {
     std::thread writer_thread(writer);
-    std::thread reader_thread(reader);
     std::this_thread::sleep_for(std::chrono::milliseconds(100));
+    std::thread reader_thread(reader);
     if (reader_thread.joinable()) {
         reader_thread.join();
     }