How to configure CRACO config file?

I want to configure the middleware of my craco.config.js, but I don’t know have, so I want tips. My actual file is:

const {CracoAliasPlugin} = require('react-app-alias')

module.exports = {
  plugins: [
    {
      plugin: CracoAliasPlugin,
      options: {}
    }
  ],
}

I found that I need to do something:

  devServer: (devServerConfig, { env, paths }) => {
    devServerConfig = {
      onBeforeSetupMiddleware: undefined,
      onAfterSetupMiddleware: undefined,
      setupMiddlewares: (middlewares, devServer) => {
        // Define middlewares
        return middlewares;
      },
    };
    return devServerConfig;
  },

But I don’t know how to use it and configure it, and I don’t want to implement any middlewares for now, just let the navigation without authentication. But, I’ll need them in the future, so, I want to know how to configure it and some tips on what is good to do here… also, if I just implement this the way is above it gives me error 404.