Get some clove oil, put fish in anonther container, add some clove oil, wait until fish rolls over. If adding clove oil fish does not roll over in a minute or two add some more clove oil. Just use a container large enough to put fish in and enough water to support and cover fish. Once fish rolls over, its in all reality knocked out so feel free to either take a knife to it and cut the head off or leave in clove oil for a long period of time (30 minutes or so, or just place in plastic bag and place in deep freeze once its knocked out.
Most times bacterial infections and fungas is totally treatable if the proper meds are used and not those so called pima or mela fix or some of that crap they sell in lfs that makes exhorbarant claims. Best is a dip in potassium permanganate which will wipe out any and all signs of fungal infections then treat with spot applications of iodine or hydrogen peroixide, apply neosporin or panalog ointment, covered with denture cream or powder to form a protective cover over worst parts of sores, and place in antibiotic doesed tank with proper gram neg or pos for what your treating. Tetracycline is the preferred choice or a broad spectrum triple sulpha.
There is a reason your fish got sick, and if its in the house ina tank along with others of decent size its a good potential its a water quality problem as thats what sets off most bacterial infections and fungal attacks on goldies...Once water is too warm or too nasty with pathogens they can catch crap pretty darn fast..and it does not take much ammonia or nitrite to give em problems. They caught the fungal infection and the bacterial is a secondary illness brought on by the fungal infection.