mkcert if you need only on one system - usually for development. step-ca/step-cli if you need a CA at residential or office domain. XCA if you don't mind a GUI and know how to get the root CA certificate into the system/browser trust stores.

links in this comment: https://news.ycombinator.com/item?id=37542794

Thanks for the links.

Let me re-phrase my question slightly:

Is there any npm-modules I can install (with npm) which would allow Node.js to automatically serve https?

I'm afraid I don't have a firsthand reply to that question. Sorry! Have you given this a try? https://nodejs.org/api/tls.html#class-tlsserver

Thanks for the link

mkcert is the easiest