mongo全局插件不可用？

[feng23030206]

项目是基于typegoose开发的，我在middware中定义了mongo的全局plugin，用于为每个schema都添加时间戳，但是不起作用，在2.x版本是好使的，升级后就不好使了，请大神指教。下面为具体代码
import * as mongoose from 'mongoose';
....
@provide()
export class orm implements IWebMiddleware {

@Inject()
conn: MongooseConnectionService;

resolve() {
return async (ctx: Context, next: IMidwayWebNext) => {
console.log(ctx.originalUrl);
console.log('全局中间件调用-controller之前');
mongoose.plugin(PreOption);
// this.conn.plugin(PreOption);

  // plugin(this.PreOption)
  // 控制器前执行的逻辑
  await next();
  //mongoose.plugin(this.PreOption)
  console.log('全局中间件调用-controller之后');
  // mongoose.plugin(this.PreOption);
};

}

PreOption(schema: mongoose.Schema) {
schema.add({ ct: Date, ut: Date });
schema.pre('save', function (next) {
this.set('ct', new Date());
this.set('ut', new Date());
next();
});
schema.pre('updateOne', function (next) {
this.updateOne({ $set: { ut: new Date() } });
next();
});
schema.pre('insertMany', function (next) {
this.set('ct', new Date());
this.set('ut', new Date());
next();
});
schema.pre('findOneAndUpdate', function (next) {
this.update({ $set: { ut: new Date() } });
next();
});
}
}