KOA中継読取ファイル戻り

static async proxyFile(ctx) {
        // let url = ctx.request.query['img'];
        let url = 'http://pic37.nipic.com/20140113/8800276_184927469000_2.png';
        // console.log(ctx.request.origin)
        let file = await super.axiso.get(url,
            {responseType: 'stream'});
        ctx.type = 'img'
        ctx.body = file;
    }