To add a further confusion to the matter, I should point out that the timing and duration of heat / cold can dramatically affect plants; as can humidity, soil moisture, soil PH and type, etc.... The only way to know for sure if it will grow in your area is to try it yourself. I have a number of plants in my yard that are rated hardy to zone 7 or 6 at most (Passiflora hybrids, Ophiopogon nigrescens, etc.) that are thriving after 15 years with no special care or siting in my zone 5 climate.
All that being said, from what I know of Tennessee's climate, I wouldn't expect any problems growing Goji berries. You'll never know until you try.