It's actually a year older than Go (2008 rather than 2009).
If you don't want to use Nim because it's not stable enough or has too small an ecosystem (I disagree), you could try out Scala Native or Kotlin Native. A large portion of their ecosystem successfully compile to native code (although you may have issues with Scala Native compile times).
You can also check out OCaml.
I have checked out OCaml but it's not mainstream enough to have libraries for... anything really. Here's the first thing I checked just now: https://www.elastic.co/guide/en/elasticsearch/client/communi...
The OCaml client was abandoned 5 years ago. Nim doesn't even appear on the page!
This page says Kotlin Native is still in preview: https://kotlinlang.org/docs/reference/native-overview.html
Also, I am not seeing a reason why Go is not a good choice.
I think you may have unnecessarily restricted yourself by wanting a language that produces native binaries and is GC'd. There simply _aren't_ that many mature and mainstream languages that compile to native binaries with a GC. I'd personally much prefer a more expressive language with a less robust ecosystem (and a virtual machine), but if an Elastic lib is a hard requirement for you, then I can't argue with your choice of Go.
Or use Haskell. Native binaries, opinionated, decent library ecosystem ;).
And it's not just Elasticsearch. That's just one example. I would come up against many other requirements. Here's just one more: https://nats.io/download
Edit: And you're right, Haskell is something I should probably look into more. I haven't thought about it too much since I already do a lot of functional programming in JavaScript and I don't hear too much about Haskell being great for creating API servers.
One of my other concerns is that the project I'm planning will be a long-haul, and will have several other developers join in future. I want to have a decent market to choose from. And, being in Australia, it's small enough as it is. I'll shy away from remote workers since it's relating to sensitive healthcare data.
Like, no, compiling to machine code is only one class of compilation. All the VM-targetting languages have far more robust ecosystems than Go, with good abstractions, performance and tooling to boot. _Any_ language that targets the CLR or JVM should suffice.
It has thousands of libraries, check opam out. If something is absent, why won't you write your own library anyway? Elasticsearch is really not that complex, here is the example:
It indicates that you haven't written one? That's a rather strange attitude, for sure it doesn't have a wrapper for any rest api, what it has is all needed tools for write it, that's what really matters. The tool in repo above does not even use a library, only generated bindings. It's much easier to write a client to a rest api in OCaml than in Go due to derivers [1], atdgen [2] and the power of the language. Take a look at graphql bindings as an example [3] [4].
[1] https://github.com/ocaml-ppx/ppx_deriving
[2] https://github.com/mjambon/atd
