Hi 
Goldfish will eat most plant as greenery is part of their diet
There are other plants you could try that will be ok in cooler water. Thicker/tough leaved plants might fair better. Like sagittaria and vallis. Amazon swords do ok in cooler water and the leaves are tougher and are supposed to nor taste too good. Some of the hygrophilas are worth a try like polysperma and difformis (water wisteria).They all grow quite fast too.
Hornwort is a well known pond plant but will do ok in a tank too. It does grow fast this time of year in ponds.
There are others that are worth a try too. It's probably a case of trial and error.
Be aware though that most lfs and online plant stores sell plants for coldwater tanks that are not true aquatics. They say they last long enough before the fish eat them, but the truth is they soon deteriorate under water and go mushy thus polluting the water. So the best thing is not to put them in there to start with in my opinion
The type of plants sold are usually dracaenas and spider plants to name but two. They are as you know well known houseplants!