(a) A summons to garnishee may be issued
(1) At the time of the issuance of the original order of attachment, by the court making such order, or
(2) At any time thereafter prior to judgment in the principal action, by the court in which the action is pending.
(b) At the request of the plaintiff, such summons to garnishee shall, at either such time, be issued to each person designated by the plaintiff as a garnishee.