Wis. Stat. § 893.75

Whenever the proper officers of any city, village or town, however incorporated, enter into any contract in manner and form as prescribed by statute, and either party to the contract has procured or furnished materials or expended money under the terms of the contract, no action or proceedings may be maintained to test the validity of the contract unless the action or proceeding is commenced within 60 days after the date of the signing of the contract.