/usr/share/gocode/src/launchpad.net/mgo is in golang-gopkg-mgo.v2-dev 2015.12.06-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gocode/src/launchpad.net/../gopkg.in/mgo.v2
/usr/share/gocode/src/launchpad.net/../gopkg.in/mgo.v2