mailer.js
-------------------------------------------------------------
const nodemailer = require('nodemailer');
const {EMAIL_ID, EMAIL_PASSOWRD} = require('../constant');

let transporter;
const initTransporter = () => {
	transporter = nodemailer.createTransport({
		service: 'gmail',
		host: 'smtp.gmail.com',
		port: 465,
		secure: true,
		auth: {
			user: EMAIL_ID,
			pass: EMAIL_PASSOWRD,
		},
	});
};

const getTransporter = () => {
	return transporter;
};

module.exports = {
	initTransporter,
	getTransporter,
};



app.js
-------------------------------------------------------------
const app = require('express')();

const {initTransporter} = require('./Utility/nodeMailerUtil.js');
initTransporter();

app.listen(3000, () => {
	console.log('listening on *:3000');
});



contact.js
-------------------------------------------------------------
const {EMAIL_ID, EMAIL_PASSOWRD, TO_EMAIL_ID} = require('../constant');
const {getTransporter} = require('../Utility/nodeMailerUtil');

exports.serviceRequest = async (req, res) => {
	let result = await getTransporter().sendMail({
		from: EMAIL_ID,
		to: TO_EMAIL_ID,
		subject: 'new service request',
		text: `Request To add service hello`,
	});
}