You can follow this:

1. run npm i --save-dev webpack-node-externals run-script-webpack-plugin webpack
2. create a webpack-hmr.config.js file in the root directory of your application and put this:

const nodeExternals = require('webpack-node-externals');
const { RunScriptWebpackPlugin } = require('run-script-webpack-plugin');

module.exports = function (options, webpack) {
  return {
    ...options,
    entry: ['webpack/hot/poll?100', options.entry],
    externals: [
      nodeExternals({
        allowlist: ['webpack/hot/poll?100'],
      }),
    ],
    plugins: [
      ...options.plugins,
      new webpack.HotModuleReplacementPlugin(),
      new webpack.WatchIgnorePlugin({
        paths: [/\.js$/, /\.d\.ts$/],
      }),
      new RunScriptWebpackPlugin({ name: options.output.filename }),
    ],
  };
};

3. inside your main.js:

async function bootstrap() {
  <Your Express middleware and etc>
  if (module.hot) {
    module.hot.accept();
    module.hot.dispose(() => server.close());
  }
}

inspired by Nest.js HMR