Short Rest (p. 186). After applying your Constitution modifier to a Hit Die roll, you regain a minimum of 0 hit points (6th printing).
I don't know if previous versions of the basic rules were updated accordingly, but at the least, the 2018 basic rules PDF (released after the 2018 errata) was updated to include this info about short rests (emphasis mine):
For each Hit Die spent in this way, the player rolls the die and adds the character’s Constitution modifier to it. The character regains hit points equal to the total (minimum of 0).