I shouldn't be, no.

loweredUid := strings.ToLower("103049322976392772444")
    stream, err := client.LookupResources(
        context.TODO(),
        &pb.LookupResourcesRequest{
            ResourceObjectType: "pandora/prn_somekey_key_keyname",
            Permission:         "sign",
            Subject:            &pb.SubjectReference{Object: &pb.ObjectReference{ObjectType: "container/user", ObjectId: loweredUid}},
        },
    )