os/user.Group.Gid (field) 2 uses os/user (current package) cgo_lookup_unix.go#L137: Gid: strconv.Itoa(int(_C_gr_gid(grp))), user.go#L62: Gid string // group ID
The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)