节点：完成所有工作后发送响应

Question

如果我拨打“http://localhost:3000/?fqn=mfgthun.ch&port=80”，那么我会收到以下字符串： {"source":"U259636","destination":"mfgthun.ch","ips":[]}

重新提交的内容应如下：
{"source":"U259636","destination":"mfgthun.ch","ips":[{"ip":"87.237.169.85","reachable":false}]}

函数Write中的部分丢失了......我是否需要在此处添加另一个回调？或者还有其他解决方案吗？

为什么在第一个app.get块完成之前不等待？

const express = require('express')
const app = express()
const isReachable = require('is-reachable');

var dns = require('dns');
var os = require('os');
var url = require('url');
var jsonResponse;

function Write (ipPort, ip) {
    this.ipPort = ipPort;
    this.ip = ip;
    this.callback = function(reachable) {
        var temp = {ip: ip, reachable: reachable };
        global.jsonResponse.ips.push(temp);
    };
}

app.get("/", function(httpRequest, httpResponse, next){
    try {
        var url_parts = url.parse(httpRequest.url, true);
        var query = url_parts.query;
        global.jsonResponse = { source: os.hostname(), destination: query.fqn, ips: [] };

        dns.resolve4(query.fqn, function (err, addresses) {
            if (err) throw err;
            for(var i = 0; i < addresses.length; i++) {
                var ipPort = addresses[i] + ':' + query.port;
                var write = new Write(ipPort, addresses[i]);
                isReachable(ipPort).then(write.callback);
            };
        });
    } catch(err) {
        console.log(err);
    };
    next();
});

app.get("/", function(httpRequest, httpResponse){
    httpResponse.write(JSON.stringify(global.jsonResponse));
    httpResponse.end();
});

app.listen(3000)