There seems to be a discrepancy between sources for the Goliath's 'Mountain Born' racial trait.
Volo's Guide to Monsters (p. 109) includes the following description for the trait:
You're acclimated to high altitude, including elevations above 20,000 feet. You're also naturally adapted to cold climates, as described in chapter 5 of the Dungeon Master's Guide.
(BTW, there is nothing in the Volo's errata PDF, last released in 2017, to correct any of that.)
However, the description of the trait on D&D Beyond's goliath race page says:
You have resistance to cold damage. You’re also acclimated to high altitude, including elevations above 20,000 feet.
Which description is correct? Do Goliaths get cold resistance from the Mountain Born trait?
Best Answer
Both are correct at the moment, depending on which sourcebook you're taking the stats from.
As RallozarX has already mentioned, the Icewind Dale: Rime of the Frostmaiden adventure includes Goliaths as a playable race and they have added cold resistance.
D&D Beyond has obviously updated the Goliath page to include the addition from Icewind Dale: Rime of the Frostmaiden.1
Volo's Guide, however, was first released in November 2016, with the only errata to-date released roughly a year later, well before Icewind Dale: Rime of the Frostmaiden which was released September 2020.
Since they can't go back in time and change the Volo's Guide Goliath, and since Rime of the Frostmaiden is so new, there is going to be that discrepancy. Whether or not cold resistance is errata'd into Volo's Guide in the future, who knows.
1: Also note that even though D&D Beyond is an official source for rules, it is also 3rd party so there is the possibility of discrepancies, especially considering the Goliath D&D Beyond page still has the Elemental Evil Player's Companion footnote.