Foraging enough mushrooms to provide any real sustenance sounds like a real challenge (except for fall in the northwest).
Forage them (safely!) in the fall, dry them out (I stick them on a wire rack over a radiator for a few days), then into an airtight jar. Toss a few into soups/sauces the rest of the year.
Once you know where patches are (at least for mycorrhizal fungi which are some of the best) it is easy to go back and get them each year. But, it still takes time to find all the locations and there is competition from other foragers, humans as well as other animals.
Actually this is a bit of a myth. Pigs aren't very good truffle hunters. Dogs are used to find truffles. I suspect this is what the GP was thinking of.