下面的代码可以保存生成的二维码图片，但打不开，不论是jpg，png，jpeg都不行
const createCodeBar = co(function* (){
const postRequest = promisify(request.post, { multiArgs: true,'json': true });

    let token = 'h3-Oda1A05Nit6EEZEkFqvgemQPCpRj1rmwYCp3puMahUH_a4rMXbYlS2NoMsjYiVhci0uDbe-VNlQAui1Ljp-fyFi8PqrGYZEsUMA0G88xmob-fheZ2c_85Jw8tnMx-NFSbAHACUH';
    console.log('token:' + token);
    let form = {
        'path':'page/bookflow/pages/sharegroup/sharegroup?groupId=279&introducer=1686&fromBarcode=true'
    }
    form = JSON.stringify(form);
    console.log(form);
    let result= yield postRequest({url:'https://api.weixin.qq.com/wxa/getwxacode?access_token=' + token,form:form});

    fs.writeFile('d:/mybar.png', result[0].body, function(err) {
        if (err) {
            console.log('出现错误!')
        }
    });
    console.log('result:' + result[1]);

})