Merge pull request #63 from Classy-Bear/master

Fix known issues: Tutorial 'Write HTTP clients & servers' doesn't workk as expected

httpserver/bin/mini_file_server.dart

@@ -39,7 +39,7 @@ Future main() async {
     } else {
       print("Can't open ${targetFile.path}.");
       req.response.statusCode = HttpStatus.notFound;
-      await req.response.close();
     }
+      await req.response.close();
   }
 }