/usr/share/go-1.8/src/os/user/ is in golang-1.8-src 1.8.3-2ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/go-1.8/src/os/user/getgrouplist_darwin.go
/usr/share/go-1.8/src/os/user/getgrouplist_unix.go
/usr/share/go-1.8/src/os/user/listgroups_solaris.go
/usr/share/go-1.8/src/os/user/listgroups_unix.go
/usr/share/go-1.8/src/os/user/lookup.go
/usr/share/go-1.8/src/os/user/lookup_android.go
/usr/share/go-1.8/src/os/user/lookup_plan9.go
/usr/share/go-1.8/src/os/user/lookup_stubs.go
/usr/share/go-1.8/src/os/user/lookup_unix.go
/usr/share/go-1.8/src/os/user/lookup_windows.go
/usr/share/go-1.8/src/os/user/user.go
/usr/share/go-1.8/src/os/user/user_test.go