我正在尝试为存储在我的私有s3存储桶中的文件创建一个预签名的url数组，但是由于res.json函数错误，我似乎无法返回它们。尽管存在相同问题的线程数量众多，但我无法弄清楚。我的代码有什么问题？

const express = require('express');
const AWS = require('aws-sdk');
let config = require('./config');
let app = express();

var s3 = new AWS.S3();
s3.config.update({
    accessKeyId: config.accessKeyId,secretaccessKey: config.secretaccessKey,region: 'us-east-2'
});



// Create an array that houses pre-signed Urls
// Loop through x amt of times (depending on number of documents)
// Push each url into an array called 'preSignedUrls'
// Exit loop and reset array to re-generate new urls
var router = express.Router();


function getSignedURL(res) {
    Key = ['file1.pdf','file2.pdf'];
    let promises = [];
    let i = 0;
    while(i < Key.length){

        var params = {
            Bucket: 'bucketname',Key: Key[i],Expires: 36000
        };

        promises.push(s3.getSignedUrlPromise('getObject',params));
        console.log(promises)
        i++;
    }
    Promise.all(promises)
    .then( response => {
        res.json(response);
    },function(err) { 
    console.log(err);
    });

}


router.route('/get_signed_url')
.get(getSignedURL);
//                 if (err) {
    // console.log(err);
    // return next(err);

router.route('/get_signed_url')
app.use('/v1',router);

var PORT = process.env.PORT || 3001;
var HOST = process.env.HOST || '11.123.346.789';

console.log("Listening on",HOST,PORT);
app.listen(PORT,HOST);

这是我得到的： (node:6717) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 5): TypeError: res.json is not a function