如何接收事件通知

const Koa = require('koa')
const Router = require('koa-router')
const bodyparser = require('koa-bodyparser');

const app = new Koa()
const router = new Router()

// 示例请求路由代码，后续会将其用正式路由替换
router.post('/hello', (ctx, next) => {
    ctx.body = 'world'
})

app.use(bodyparser());
app.use(router.routes())
app.listen(80)

const fileCreatedEventType = "Storage.NewFileCreated"

router.post('/Callback', async cxt => {
    //获取post传递的数据
    const body = cxt.request.body
    const eventtype = body.EventType
    if (eventtype === null) {
        console.log("invalid EventType")
        ctx.body = {
             Code: "Failed",
        } 
        return
    }

    switch (eventtype) {
        case fileCreatedEventType:
            const event = body.StorageNewFileCreatedEvent
            console.log("MaterialId: " + event.MaterialId)
            console.log("FileId: " + event.FileId)
        default:
            console.log("EventType: " + eventtype)
    }

    ctx.body = {
         Code: "Success",
    }
});