Several things.
1: Darius is a natural pain to deal with as any melee champion. Especially squishy ones like Shaco.
2: Shaco is not a good solo laner. He loses all of his advantages of crazy early game ganks and map presence.
3: Darius is really hard to itemize against because he does all 3 types of damage. physical, magic, and true damage. If you need to build defensively against him, get health.
I've dealt with a Shaco as Darius before, and it wasn't pretty for them. I managed to snowball 9 kills in lane and carry the team. Shaco is NOT a solo laner, stick to the jungle with him and you'll have a much higher chance of success.