Tekao.net now uses Letsencrypt! Let's Encrypt issues short term certificates, three months i think, for websites that can prove they own a domain. You can check the letsencrypt.org certificate for the page you are reading now by clicking on the padlock to left of the address bar in your browser.
Using rsc.io/letsencrypt it's extremely simple to have a Golang webserver that uses the standard HTTP package be supported. It all happens on demand with no configuration: Given a HTTPS request to your server, it will ask for a certificate and prove to Let's Encrypt that you own the host whose name is specified in the request. It proves this by serving specific content reachable from Let's Encrypt servers using the host name.
This certificate will be used on subsequent requests. I guess until it expires.
Check out Let's Encrypt website for details of the certificate issuing protocol.