Assuming you cd into your folder and the error still persists, try running "bee version".
bee :1.2.4
beego :1.4.3
exec: "go": executable file not found in $PATH
What you need to do is to rename "go_appengine/goapp" to "go_appengine/go".
And rename "go_appengine/goroot/goapp" to "go_appengine/goroot/go".