AccessTokenUtil.js

const request = require('request'),
    uuidv4 = require('uuid/v4');

let arguments = process.argv.slice(2)
if (arguments.length != 2) {
    console.log("Usage: npm start <user> <password>")
    process.exit()
} else {
    let user = arguments[0]
    let password = arguments[1]
    console.log("Generating Auth UUID...")
    let uuid = uuidv4()
    console.log("Generated UUID/v4 %s", uuid)

    console.log("Building request payload...")
    let payload = {}
    payload.agent = {
        "name": "Minecraft",
        "version": 1
    }
    payload.username = user
    payload.password = password
    payload.clienttoken = uuid

    let options = {
        uri: "https://authserver.mojang.com/authenticate",
        method: "POST",
        json: payload
    }

    console.log("Executing request...")
    request(options, function(err, response, body) {
        if (!err && response.statusCode == 200) {
            let accessToken = body.accessToken
            console.log("Access Token: " + accessToken)
        } else {
            console.error("ERROR: " + response.body.errorMessage)
        }
    })
}