I have been thinking about getting a golden retriver
Thats great!, I own 5 of them, Mine are well suited to pretty much all suburban or country environments. We have moved around quite a bit lol. 
How big do they get?
Well most of them grow to around 3 feet tall and weigh about 60 pounds usually But ive seen bigger ones, 
That is pretty big im not sure my apartment can handle that
Also they shed copiously, around the change of seasons usually, and require regular grooming. You might have a lot of fur in your apartment, So have a vacuum handy. 
Yeah I have a cat but he doesnt shed really. 
My dogs really like cats, They seems to be great companions and I keep one cat around ability to hunt the vermin in my house which my dogs cant do.