[bluk]

I've pushed a few admittedly minor backend services in Swift to production. It is ok.

You basically have one viable non-Apple OS platform (Ubuntu) to deploy on. This means that your basic Golang service is a 10MB Docker image while it can be over 100MB for a basic Swift service. There are frameworks like Swift NIO which is based on Java's Netty (and there are some Apple developers who work on Netty also working on Swift NIO). It works well enough but in most benchmarks, Swift is not even close to Netty ( https://www.techempower.com/benchmarks/#section=data-r18&hw=... ), so if you're pushing the code expecting high performance, I would think twice. Swift gRPC (latest version based on Swift NIO) is also available, and while I think it works very well, it is still relatively new.

As far as tooling, Swift is very immature IMO if you step outside Xcode. There are efforts to get a LSP service fully working (SourceKit-LSP), but I find it to be ok at best (performance and code completion suggestions are often very hit or miss). From benchmarking to diagnostics/backtraces to logging and metrics frameworks to shared common knowledge/answers on Stack Overflow, it is still very early days for Swift. Golang is so far ahead here that I personally think (at least today) the only reason you should launch a Swift service into production is because you want to reuse code that you have in your app.

If you like Swift's type system and want a backend service equivalent, I would strongly recommend looking into Rust. IMO, Rust is a version of Swift where the programmer is given more control of what the code is actually doing (along with the associated responsibility). It sounds like a lot of trouble, but I find most Swift code naturally translates to Rust code (especially if you follow the "value vs reference" semantics ideology that the Swift compiler team advocates). At worst, if you learn Rust, you will understand Swift a lot better (like what really is an escaping vs. non-escaping closure or what is the difference if I use a generic versus a dynamic protocol type (dyn trait in Rust) in a function definition).