Newts or Axolotl with Goldfish?

As long as one can`t eat the other you should be alright.

try it and see what happens. That said, keep an eye on your goldfish. If they are small enough for your axolotl to eat he most probably will. Also keep an eye on the axolotl. Sometimes its actually your mudpuppy that has to worry. Certain fish will pick at his gills and harrass him. I doubt that problem will occur with goldfish, just putting it out there in case you get something else going forward. have fun.

Depending on the temperature of the tank. Axolotls need sub 65f to thrive. The goldfish will get eaten unless they are large, to which point they might nip at the axies gills. Axies are best kept alone, or in well monitored groups.