We can't directly return a value in koa, so the front-end can't get this value
We need to mount the value (mostly json in actual development) ctx.body, so that the front end can get the data.
If we return an object, koa will automatically convert this object into a json object and add it to the Response HeadersContent-Type: application/json
koa-router
The use of koa-router can be divided into these three steps:
