Changed various locking mechanism.

Store/ChatterGroupStore.cs

@@ -30,7 +30,8 @@ namespace HermesSocketServer.Store
             await _database.Execute(sql, data, (reader) =>
             {
                 var chatterId = reader.GetInt32(0).ToString();
-                lock (_lock)
+                _rwls.EnterWriteLock();
+                try
                 {
                     _store.Add(chatterId, new GroupChatter()
                     {
@@ -40,6 +41,10 @@ namespace HermesSocketServer.Store
                         ChatterLabel = reader.GetString(1),
                     });
                 }
+                finally
+                {
+                    _rwls.ExitWriteLock();
+                }
             });
             _logger.Information($"Loaded {_store.Count} group chatters from database [group id: {_groupId}]");
         }