A question is what you would consider a more mature environment? E.g. C++ - a decades old programming language - does not contain widely accepted solutions for building web services. There are some libraries, but I mostly have not seen them being used outside of the companies that developed them. I think Rust already has a better stance there.
Probably Go and node.js could be counted as good solutions, because their standard libraries cover the use-case very well. Or Java, thanks to a mature ecosystem around web services - even though the mainstream solutions (Servlet) focus on blocking IO.
I like node for really fast productivity, at the cost of a little potential stability... not the absolute best performance, but usually good enough.
Up from there would imho be Go or C#, mostly because they're faster than node, but still very accessible, and really good support around them for web services. Certain workloads are still not great. I think Java is probably okay, I just personally don't care for it, apparently it's gotten better than when I last used it regularly over a decade ago.
Rust is when you want balls out absolute performance in a language with newer, higher level features and constructs. The unsafe escape hatch is really there if/when you need it, but should not be the norm. The final executable size on rust is also impressive and will work very well in some constrained environments, or when you need better execution performance and more control than the others provide (outside of C/C++, D and a couple others).
I've only built a couple smaller web apps with rust so far, but the output size is impressive. Being able to build to a bare container or with busybox if some in-container scripting is needed has been a great experience so far.
Probably Go and node.js could be counted as good solutions, because their standard libraries cover the use-case very well. Or Java, thanks to a mature ecosystem around web services - even though the mainstream solutions (Servlet) focus on blocking IO.