What makes a server production ready?

For me the reason to use nginx is ease of configuration. Recreating that kind of configuration in code is possible, but tedious and time-consuming.

Adding to what others have said, I mentioned 'production-ready' specifically because built-in http servers in programming languages are usually for testing and are not supposed to be used in production due to poor performance e.g. Python's http server and hence you'd require a standalone http server with python or Node.js applications.

In Go you can use default http server, multiplexer and router to serve your http requests directly to your application logic. It also has support built-in for Lets Encrypt SSL certificate via autocert covering all fundamental reasons you'd want a standalone web server for your web application.

Production ready things are scalable, you can make them highly available, and they are reliable.

Microsoft wants to have a word with you.