The salary or wages of any county, city, town, or school district official or employee for services rendered or labor performed for the county, city, town, or school district before the service of a writ shall be subject to trustee process. The trustee writ shall be served upon the county, city, town, or school district treasurer who shall be chargeable as any other trustee; provided, however, that if the writ is duly entered in court, the treasurer shall discharge himself by paying to the clerk of that court such portion of said salary or wages as is due or payable at the time of service of said writ on the treasurer; and provided further, that the county, city, town, or school district treasurer shall not be chargeable unless the writ shall be served upon him before the check for such salary or wages has left his custody.