How can I mock or simulate gRPC APIs?

I am doing a lot of manual exploratory testing of microservices after a feature story has been delivered. To do that, I need to simulate different responses from a gRPC API. So I would like to start a docker image with my microservice, and point it at a gRPC API that I can control and simulate different types of responses to test different sad-path scenarios.

How can I create mocks of gRPC APIs?