@mbernal/nodejs-create-react-app/middleware/express/createReactApp.js

const paths = require("../../config/paths");
const path = require("path");

module.exports = ({app,express})=>{
    const serverRendering = app.get('view engine');


    app.get('/health', function (req, res, next) {
      //TODO: Put some kind of actualy deeper check to make sure server is still healthy.
      return res.status(200).json({statusCode:200});
    });

    app.get('*', function (req, res,next) {

      //Handle Server Rendering is enabled on the server
      if(serverRendering){
        
        let errors = "";
        
        if(req.session && req.session.error){
          errors = req.session.error;
          delete req.session.error
        }

        return res.render('index', Object.assign({
          layout:false,
          errors:errors,
        },res.locals));
      }

      //No server rendering assume html is build dir
      res.sendFile(path.join(paths.appBuild, 'index.html'),{},(err)=>{
        if (err) {
          res.sendFile(path.join(paths.appMiddleware,"express","NotFound.html"));
        } 
      });
    });

    return app;
}