add logger

main.cpp

@@ -93,7 +93,7 @@ void RunWorkers(unsigned n, const Fn& fn)
 int main()
 {
   Logger::GetInstance().SetOutStream(cout);
-  Logger::GetInstance().Log("Qwerty"s, 2, 3, 14);
+  Logger::GetInstance().Log("Server started");
 
   const unsigned num_threads = std::thread::hardware_concurrency();
 

src/Logger.h

@@ -53,7 +53,7 @@ class Logger
   template<class First>
   void LogImpl(First fst)
   {
-    *stream_ptr_ << fst;
+    *stream_ptr_ << fst << '\n';
   }
 };
 }  // namespace http_server