How to sent Content-Length on a HEAD response

[ajmichels]

I am trying to sent the Content-Length header of a HEAD method response but it seems like Koa it automatically removing the header when the body is set to null. I am sure there is some trick to this that I am just not familiar with but I can't figure out what it is.

export async function head(ctx, next) {
    ctx.set('Content-Length', Buffer.from(JSON.stringify(ctx.body)).length);
    ctx.body = null;
    await next();
}

Note: ctx.body is originally being set in a middleware function that runs before this one.

[jonathanong]

try setting the content length after setting the body