If you are are having trouble setting up Fragmenta CMS (or any other Go app, for that matter), the following info will be useful.
The $GOPATH variable must be globally set. That means that you must not set it on a "per project" basis. Usually, it defaults to "$HOME/go".
The root directory of every Go app that you create must be a directory in the "$GOPATH/scr" directory.
So, if you are trying to create a Fragmenta site, you must create a directory within "$GOPATH/scr".
mkdir -p $GOPATH/scr/fragmentaSite
fragmenta new cms src
to create the app within the "src" directory of the "$GOPATH/scr/fragmentaSite" directory.