I cannot locate a setting in the Gmail app to disable this feature, but you can disable it via a laptop or PC
Log in to your Gmail account, click on the cogwheel in the upper right corner of the screen and choose settings.
Under the General tab look for "Create contacts for auto-complete" and put a tick in the box for "I'll add contacts myself".
Not sure if there's a setting in Go Contacts that would affect what you describe. Have you checked all of it's settings?
Hope this helps!