Contrary to its name, Goatskin isn't a goat in Kingdom Come: Deliverance 2. He's a crucial character you must locate during the "Into the Underworld" main quest in Kuttenberg. Katherine will direct you to the inn, but finding him involves a bit of detective work. Here's a simpler approach:
Goatskin is located in the barn above the Black Horse tavern. Access the barn behind the tailor's shop and climb the ladder. Remember, this is a private area, so stealth is key.
Once upstairs, drop down into the courtyard, climb onto the carriage, and enter the adjacent barn through the window. Continue to the top floor; Goatskin will be there. This method only works during the day; he changes locations at night. Saving your game beforehand is recommended, as you'll need to succeed in several dialogue checks to avoid hefty bribes (150 groschen initially, rising to 500 groschen upon failure).
Failing the skill checks will cost you 500 groschen, a substantial sum. If you're unsure of your success, paying the initial 150 groschen is a safer bet.
That's how to find Goatskin in Kingdom Come: Deliverance 2. For more game guides, including romance options and optimal perk selections, check out The Escapist.