我在文件server1.js中有一个快速服务器，在文件server2.js中有另一个服务器。我想知道如何在Server1 addUser api中调用Server2 getUserId API？
server1.js

// Server1
const express = require("express");
const app = express();

app.get('/api/addUser/:userName', (req, res) => {
    const user = {
      userName: req.params.userName,
      userId: // call to getUserId api to get userId from server2
    };
    users.push(user);  
    res.json(`user addedd: ${JSON.stringify(user)}`);
    });

app.listen(3000, () => {
    console.log("Listen on the port 3000...");
});

Server2.js

// Server2
const express = require("express");
const app = express();

app.get('/api/getUserId', (req, res) => {
    res.json(Math.random());
    });

app.listen(3001, () => {
    console.log("Listen on the port 3001...");
});