REST and gRPC API design patterns for Go services. Covers HTTP handlers, middleware, routing, request/response patterns, versioning, pagination, graceful shutdown, and OpenAPI documentation. Use when designing APIs, writing HTTP handlers, implementing middleware, structuring REST endpoints, or setting up gRPC services. Trigger examples: "design API", "REST endpoints", "HTTP handler", "middleware pattern", "graceful shutdown", "gRPC service", "API versioning". Not for: general architecture (go-architecture-review), concurrency in handlers (go-concurrency-review).
