In addition to other feats taken at 1st level, as a Goliath you may take this feat as a replacement for the Giant Ancestry feature.

You ancestry includes Troll, warped kin of true Giants, and carry their unsettling gift for regeneration. Scars are rare — wounds knit shut and fade away. Some with this heritage are shunned; others are feared or respected for surviving what should have killed them.

Giant Ancestry

You can use the chosen benefit a number of times equal to your Proficiency Bonus, regaining all expended uses when you finish a Long Rest.

At the start of your turn, you can choose to regain Hit Points equal to 2d6 + Proficiency Bonus without using an action. You can't use this feature if you took acid or fire damage types since the end of your last turn, and any Hit Points lost to those types can't be restored with this feature.

You can't regenerate lost body parts, and loss of a head is fatal. When you regenerate to your maximum Hit Points, there are no lingering scars or bruises from the damage you've healed using this feature.

Death’s Door

If you start your turn with 0 hit points and are not Dead, you can use this feature before making a Death Saving Throw.