最近在学习微信公众平台开发。使用koa2.0，ctx.body = "success"这一句在注释处能正确返回给微信，回调函数能执行但是微信接收不到。

let fn_getInfo = async(ctx, next) => {
    let reqString = "";
    ctx.req.on('data', (chunk) => {
        reqString += chunk;
    });
    ctx.req.on('end', () => {
        const xml2js = require('xml2js');
        xml2js.parseString(reqString, { explicitArray: false }, (err, result) => {
            console.log(JSON.stringify(result));
            ctx.body = "success";
        });
    });
    //ctx.body = "success";
}