A snippet for Medium post: https://medium.com/@apechkurov/request-id-tracing-in-node-js-applications-c517c7dab62d

medium-cls-context-example.js

'use strict'

// a primitive logger object
const logger = {
  info: console.log
}

const express = require('express')
const uuidv4 = require('uuid/v4')

const app = express()

app.get('/', function (req, res) {
  req._id = uuidv4(); // generate and store a request id
  logger.info(`Started request handling, request id: ${req._id}`)
  
  // pass `req` object into the nested call
  fakeDbAccess(req)
    .then((result) => res.json(result))
})

async function fakeDbAccess (req) {
  return new Promise((resolve) => {
    setTimeout(() => {
      logger.info(`Logs from fakeDbAccess, request id: ${req._id}`)
      resolve({ message: 'Hello world' })
    }, 0)
  })
}

app.listen(3000, (err) => {
  if (err) {
    logger.err('The app could not start')
  }
  logger.info('The app is listening on 3000')
})