Fixed gopath issue

Go was installing properly but there were 2 problems.

First, the GOPATH environment variable was not being set properly. It actually should be set to /home/codio/workspace. 

Second, the $GOPATH/bin directory should be added to the PATH variable. When you write go code and run go install, it will create an executable and put it in the $GOPATH/bin directory. By adding this to the path, it makes it easy to run your code from any location.