go-kit/kit ? reverse-engineered prompt

Build me a Go toolkit for microservices that gives me the common building blocks I’d need to ship real services without wiring everything from scratch.

I want reusable pieces for things like request endpoints, logging, metrics, rate limiting, circuit breaking, service discovery, tracing, auth, and transport helpers, so I can combine them in different services as needed. It should feel like a practical library for building small services or a larger monolith, with clear examples that show how the pieces fit together in a real app.

Please make it work well with existing infrastructure, keep the parts loosely coupled, and avoid forcing one specific way of doing deployment or configuration. If anything needs current documentation or best practices from the Go ecosystem, look them up online and use that.