UseWebpackDevMiddleware聚合异常

https://marczak.io/posts/netcore-vuejs/

启动项目时,我遇到以下异常:

An exception of type 'System.AggregateException' occurred in System.Private.CoreLib.dll but was not handled in user code: 'One or more errors occurred.'
 Inner exceptions found, see $exception in variables window for more details.
 Innermost exception     Newtonsoft.Json.JsonReaderException : Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)

        app.UseWebpackDevMiddleware(new WebpackDevMiddlewareOptions
        {
            HotModuleReplacement = true
        });

似乎某个JSON文件的格式不正确?!但是哪一个呢。我是新的NPM和网页包的东西。