goldfish arent a true coldwater species, this belongs to trout and salmon.
goldfish are temperate water fish which means fluctuation. they can survive at most temperatures. the colder end of the thermometer they slow down and can go torpid through the coldest months (the exception being wakin, which can be seen swimming around under ice in the coldest months). at the other end they grow faster and need constant care, such as more oxygen and high energy food. goldies can and do live the warmer end of the temperature scale, but the metabolic rate is speeded up. whether this means a shorter life i dont know.
and in china and japan, all types of goldies and koi are bred in different regions, not necessarily hot.