Like Go, C# has also always been a decade behind on the tooling side. For a recent project I wanted very fast HTML templating and I/O. Went with C# instead of Go and it's looking pretty good so far. The tooling is close to the level Ruby was ten years ago, and that was really acceptable. I was very happy with my previous project that I did in Go as well, you just can't go wrong with Go for implementing network protocols.

If you need more than a microservice, then you need more than Go in my opinion, and C# is an excellent choice. I think most of these startups going mono-lingual on Go are going to regret it, just like the startups that went mono-lingual on Node.js a decade ago.

If you're building anything that requires some serious architectural structure, and that might be easiest to implement as a monolithic app, then you need a language that supports that instead of getting in the way. Now with Typescript Node.JS might finally be suitable. But I'd definitely consider Ruby and C# or maybe Java or even Haskell first. Maybe Elixir, I heard that's still going strong as well.