Dotenv-expand adds variable expansion on top of dotenv. If you find yourself needing to expand environment variables already existing on your machine, then dotenv-expand is your tool.
npm install dotenv --save
npm install dotenv-expand --save
As early as possible in your application, require dotenv and dotenv-expand, and wrap dotenv-expand around dotenv.
var dotenv = require('dotenv')
var dotenvExpand = require('dotenv-expand')
var myEnv = dotenv.config()
dotenvExpand(myEnv)
See test/.env for examples of variable expansion in your .env
file.