agent ??= new https.Agent({ ...this.client.options.http.agent, keepAlive: true });

So I'm learning how to make bot on discord using discord.js

this is my bot.js

require("dotenv").config();
const { Client } = require('discord.js');
const client = new Client();
client.login(process.env.DISCORD_TOKEN_KEY);

this is my package.json file:

{
  "name": "aibot",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node ./src/bot.js",
    "dev": "nodemon ./src/bot.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "discord.js": "^13.2.0",
    "dotenv": "^10.0.0"
  }
}

So when I run node ./src/bot.js I am getting this error:

PS E:\RIYA\AIBOT> node -v
v14.18.0

PS E:\RIYA\AIBOT> node ./src/bot.js
E:\RIYA\AIBOT\node_modules\discord.js\src\rest\APIRequest.js:33
    agent ??= new https.Agent({ ...this.client.options.http.agent, keepAlive: true });
          ^^^

SyntaxError: Unexpected token '??='
    at wrapSafe (internal/modules/cjs/loader.js:1001:16)
    at Module._compile (internal/modules/cjs/loader.js:1049:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)
    at Module.load (internal/modules/cjs/loader.js:950:32)
    at Function.Module._load (internal/modules/cjs/loader.js:790:12)
    at Module.require (internal/modules/cjs/loader.js:974:19)
    at require (internal/modules/cjs/helpers.js:93:18)
    at Object.<anonymous> (E:\RIYA\AIBOT\node_modules\discord.js\src\rest\RESTManager.js:4:20)
    at Module._compile (internal/modules/cjs/loader.js:1085:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1114:10)

What shall I do? I don't know much about NodeJs and I'm not able to figure out how to solve this issue.