Every railroad company, in making contracts for the building of its road, shall require sufficient security from the contractors for the payment of all labor thereafter performed in constructing the road by persons in their employment. The company is liable to the laborers employed for labor actually performed on the road if they, within 20 days after the completion of the labor, in writing, notify its treasurer that they have not been paid by the contractors, but the liability terminates unless the laborer commences an action against the company within 6 months after giving the notice.   [PL 1987, c. 141, Pt. A, §4 (NEW).]