I am happy to announce that I have added a custom domain name to my github pages using Hugo. I had been written a Turkish blog on how to use Hugo and integrate it with the github page.
I encountered some diffuculty when I adding custom domain. Firstly, I just added domain address from settings. But you know its not work first time :) There is an error that occur Https. In order to solve, I watched some videos from youtube. They are explain how to github add a custom goddaddy domain. Thus, I tried them. It worked. My github page is running :) But I forget to change to baseurl from hugo site config file. Finally I changed baseurl and my site is running properly :)