Having introduced Goa into a number of projects over the 18 months, I've wanted to shout about this toolchain for a while.
Goa allows you to design your APIs with a DSL, then generate an OpenAPI or Protobuf schema from the design. You can trust those specs match your API as Goa produces Go backend interfaces too, which makes it even more attractive to use tools like openapi-generator to produce clients.
If your API is used by a frontend, you can use TypeScript clients to get type-safe frontend forms against your API, turning typos into compiler errors.
This post can help you introduce Goa to your project, and explains why it's such a productivity boost.