zvash/bgmood-api-gateway ? reverse-engineered prompt

Build me a simple API gateway service in Go for a project called bgmood api gateway.

I want a clean backend app that starts from the main file, reads configuration from an env file, and runs well in Docker. Since the README does not explain the product yet, just set up a solid gateway style service with a sensible structure, basic routing, and placeholders for forwarding requests to downstream services later. Make sure it is easy to run locally with the provided start script and Makefile, and that the app boots without extra manual setup.

Please keep it practical and production friendly, with clear logging, basic health check endpoint, and good error handling. If anything is unclear, use current docs online and make reasonable choices. The goal is to have a working base I can extend into a real gateway without redoing the setup.