nixd: disable concurrent parsing as it may cause outdated / null AST

nixd/lib/Controller/Support.cpp

@@ -93,16 +93,7 @@ void Controller::actOnDocumentAdd(PathRef File,
           ShmName, ".", ".", static_cast<std::int64_t>(Buf.size())});
     }
   };
-  if (LitTest) {
-    // In lit-testing mode we don't want to having requests processed before
-    // document updates. (e.g. Hover before parsing)
-    // So just invoke the action here.
-    Action();
-  } else {
-    // Otherwise we may want to concurently parse & serialize the file, so
-    // post it to the thread pool.
-    boost::asio::post(Pool, std::move(Action));
-  }
+  Action();
 }
 
 Controller::Controller(std::unique_ptr<lspserver::InboundPort> In,