How to pass .env file variables to webpack config?

I am new to webpack and worked out almost all build sections, but now the problem is that I want to pass the environment variables from a .env file to webpack config, so that I can pass that variables to my build files via webpack.DefinePlugin plugin.

Currently I am able to to pass environment variable directly from webpack to to my build. Please see the code below which I used in webpack.

new webpack.DefinePlugin({
            "API_URL": JSON.stringify("http://my-api.com"),
            "FRONT_END_API_KEY" : "MYFRONTENDKEYGOESHERE"
        }),

My package.json build script is

"scripts": {
    "start": "NODE_ENV=development webpack-dev-server --progress --port 8000 --content-base app/build/src"
    } 

You can use dotenv package for this purpose.

npm install dotenv --save

After installing the package, add this in the top of your config:

const webpack = require('webpack'); // only add this if you don't have yet

// replace accordingly './.env' with the path of your .env file 
require('dotenv').config({ path: './.env' }); 

then in plugins section, add this:

new webpack.DefinePlugin({
  "process.env": JSON.stringify(process.env),
}),