I'd also go with Go, just because of the amazing standard library. The ability to reuse part of Google's production code for HTTP / JSON is a huge win in my book.

Also, Go has been around for long enough that you'll find libraries and tutorials even for rare issues. When I evaluated Rust, I was missing that. Their ecosystem, while highly motivated, isn't mature enough yet for infrastructure level code.

You should choose rust for the long term. The type system will pay off any initial investment. Trust me, I am maintaining a large python code base. The number of problems that appear "organically" and would have been caught with a good type system is staggering.

I don't like Python personally but even I can see the problem here is you're doing Python wrong. Look up "type annotations" and include them as part of your tox testing.

Also, as I've commented elsewhere, if what you want is a static type system then there is still a plethora of better languages for web development than Rust. Rust might be a hugely impressive language but it's not yet ready for prime time web development.