Mechanic cannot seem to fix turn signals indicators?

Over several months, I noticed my turn signal green light indicator on dashboard stopped working. First it was periodically, then it was daily. They would work when first started car then stopped. My mechanic replaced turned signal switch. Before I could get down the street from his shop they stopped working again. Brought it back and he said it was the relay. When I first started the car, the signals worked, then once again as I drove away, they stopped. I am so frustrated, near tears, and out of $300. I almost had an accident because I couldn’t put signals on. It will be very challenging getting home tonight. Any advice on what can be wrong? Should I take it to another mechanic? Live in Rockville Maryland.