/usr/share/gocode/src/ is in golang-gopkg-guregu-null.v2-dev 2.2+git20150913.0.4ac4f00-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gocode/src/gopkg.in/
/usr/share/gocode/src/gopkg.in/guregu/
/usr/share/gocode/src/gopkg.in/guregu/null.v2/
/usr/share/gocode/src/gopkg.in/guregu/null.v2/bool.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/bool_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/float.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/float_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/int.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/int_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/string.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/string_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/time.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/time_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/bool.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/bool_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/float.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/float_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/int.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/int_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/string.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/string_test.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/time.go
/usr/share/gocode/src/gopkg.in/guregu/null.v2/zero/time_test.go