nodejs KOA request pipe 同步下载图片

request pipe 是异步下载图片的，如果需要同步需要添加一个Promise

var myP = new Promise(function (resolve, reject) {                var stream = request(mainItem.pic).pipe(                    fs.createWriteStream(filepath)                );                stream.on('finish', function () {                    resolve("OK123");                });            });            var resultStr= yield myP;