To eliminate the warnings I configured vim and git to work the way golang likes.
The following command stops git from trying to do what is normally the right thing: standard line-endings in repo, platform line-endings on each developers working directory, convert as needed.
git config core.autocrlf false
Now git won't change
crlf on checkout or bleat about line-endings.
au FileType go setl ts=3 sw=3 nowrap nu syntax=go ruler fileformat=unix
fileformat=unix seems to keep vim complaint-free regarding line-endings that are not native to the platform.
3 months after posting the above question I haven't come across any drawbacks or problems - at least not the way I use