If, and only if Goblin Slayer appears, he dies both rounds. Geralt has range, experience, skill, power and reflexes to defeat him and in round 2 he could knock him over with Aard, slow him with Yrden, confuse him with Axii, deflect his attacks with Quen or simply roast him with Igni.
But since Geralt is no goblin there will be no fight.
Goblin Slayer has other things to do.
A goblin killing contest between them would be fun though