How did Gin generate SSL certificate for me although port 80 and CNAME are blocked?

[mikolajlubiak]

I've been trying to get a SSL certificate, but my ISP blocks port 80 and my domain service doesn't allow to set CNAME records.
As I way about to give up I stumbled upon autotls and it magically generated a certificate for me.

My question is: How?
Can someone explain this to me?

(https://stackoverflow.com/questions/76968320/how-did-gin-generate-ssl-certificate-for-me-although-port-80-and-cname-are-block)