I guess that you needn't have looked at the environment variables (go env) since it was installed in a different way. You should have moved on to the Zap connect part. Let's try to fix that. Type in the following commands.

sudo rm -r /usr/local/go - to make sure that the folder you have moved is completely deleted
sudo apt-get remove golang - completely getting rid of everything related to the Go. I don't think that purge command is necessary here.
sudo apt-get install golang

Please, let me know if this has worked for you. I am going to bed soon.

Edit: Oh, you have just changed your post. I will answer it in a moment.