I agree. I believe is scapegoating too. The guy that wrote the mail had no clue about anything technical, and the other guys that help him explain, didn't really understood what the programmer did and perhaps wasn't even a Go dev. And it seems that the original developer just left and doesn't want anything to do with the game anymore. So...they blame it on the language and 3th party hobby libraries from github because they can't set up the project right. That shit happens on any language even with inhouse built libraries if you put unskilled people to to the job.
