This is really cool! Go is so dead simple to learn but it just lacks a few features. I feel this really fills that specific gap.

Go with more expressive types and a bit stricter compiler to prevent footguns would be a killer backend language. Similar to what TypeScript was to JavaScript.

My 2 cents would be to make it work well with TypeScript frontends. I think TypeScript is so popular in backends because 1. you can share types between frontend code and backend code and 2. it's easy for frontend devs to make changes to backend code.