About changing the API struct, e.g: muti-return with err.

[atlas-comstock]

	iter := query.Iter(conn)
	if iter.Error() != nil {
		log.Panicln(iter.Error())
	}

I think it would be better that iter use muti-return val, which is golang API usually do.

	iter, err := query.Iter(conn)
	if err != nil {
		log.Panicln(err)
	}