How long do you soak goldfish food?

I think it depends on your food--I soak BioBlend about 5-10 minutes, I soak Hikari pellets for 20 minutes, then squeeze them so they'll sink.

I do not soak any of my goldfish foods. Feeding dry foods does not cause swim bladder troubles, it only brings out symptoms in fish that already have it.
In the past i soaked any food i gave to my floaty moor and lionhead, but presently none of my fish have this trouble.

i dont soak mine too
is it true that dry foods dont cause swim bladder
i got the impression that it does?

Dry foods are not good fed unsoaked if you have fish which are prone to swimbladder trouble. They don't actually cause SBD (although I suppose if you fed nothing but unsoaked dry foods for a very long time then they might) but they can - as Luke said - bring out the symptoms if susceptibility to SBD is already present.

Thing is, it's often impossible to tell if your fish are prone to SBD... so soaking the food first is safer.

I always soak my Tetra pellets for a couple of minutes (because they swell so much in water and I'd rather they did not swell inside my fish), though admittedly I don't bother soaking flake.