`ctx.res.headerssent = true 'appears before expected
Hi, I am implementing a nodejs framework based on koa2, but I have a problem. When I call async function in controller in depth, 404 status code appears on the page.

Through the investigation, I found that `ctx.res.headersSent` In my execution `ctx.body=data` Before it became true

I don't know what to do. I need help. Thank you.

framework url: https://github.com/keverjs
example url: https://github.com/keverjs/kever-example

**Operation steps**
1. git clone https://github.com/keverjs/kever-example
2. npm install
3. npm run dev