No clerk, servant, agent or employee of any person accused of a violation of the laws to promote temperance and to suppress intemperance or prohibiting the sale, manufacture or other disposition of liquors or beverages shall be excused from testifying against his principal for the reason that he may thereby incriminate himself, nor shall any principal be excused for the same reason from testifying against any clerk, servant, agent or employee in such cases, but no testimony given by any of said parties shall in any manner in any prosecution be used as evidence, directly or indirectly, against him, nor shall the party testifying be thereafter prosecuted for any offense so disclosed by him.