Goliath Constitution (5e Feat)
From D&D Wiki
Prerequisites: Goliath Race 
Goliath Brutal Constitution
As a Goliath, your heritage usually has it's root in strength, but it also has it's root in high constitution and a naturally high defense in this case, you have tapped into one part of that more physical heritage.
Tapping into the power that lies waiting inside you, you gain a plus 1 to Con to the max score of 20 and gain advantage on Con checks and Con saving throws.
Alternatively, you can tap into the hidden defensive ability you have. Your skin hardens and becomes rough, allowing you to add your Constitution modifier to your armor, be it heavy, medium, or light armor.
- D&D 5e Volo's Guide to Monsters pp. 108-109