Response headers will be ignored/removed while using ctx.throw.

ctx.set( 'Access-Control-Allow-Origin', '*' );
ctx.throw( 404 );

By using the code above, the header of Access-Control-Allow-Origin will not be sent with responding. Even though I can use res.statusCode instead, but I think the ctx.throw method should not remove response headers.

Koa@2.4.1 Node@8.9.3

[mutoe]

According to my usage, you also put it in the try block like this

app.use(async (ctx, next) => {
  try {
    ctx.set('Access-Control-Allow-Origin', '*')
    await next()
  } catch (err) {
    ctx.set('Access-Control-Allow-Origin', '*')
    ctx.status = err.status
})

Otherwise, there will be no header you set in the normal code.

[niftylettuce]

Feel free to use https://github.com/ladjs/koa-better-error-handler.