snap: Fix go plugin build failure by renaming go.mod
snap: Fix go plugin build failure by renaming go.mod

as a temporary workaround.

See https://forum.snapcraft.io/t/go-plugin-go1-11-fails-if-go-mod-exists-in-the-top-level-directory/7546
and https://discourse.gohugo.io/t/hugo-0-48-released/13908/12

anthonyfok/hugo,mdhender/hugo,anthonyfok/hugo,fedelibre/hugo,gohugoio/hugo,mdhender/hugo,fedelibre/hugo,mdhender/hugo,mdhender/hugo,anthonyfok/hugo,fedelibre/hugo,gohugoio/hugo,gohugoio/hugo,fedelibre/hugo