> So what is the benefit?

A better type system(covariance, dependent types) than Go's and generics, a richer ecosystem, deploying the same codebase on the server and in the client...

What's even the point of using Go? If it's for static typing Rust has that

So what's the benefit?

Same can be said about any language really, it's personal preference

If you wrote a browser client in Javascript / Typescript, then it makes sense to write a backend in it as well since it's easy to share code and data between them.

Now you can also write CLI tools that are trivial to deploy and can also share code with everything else.

This is the same motivation behind other languages that do the reverse; compile to JS / WASM.

Guessing here - is there any value from a team / engineering point of view to having shared code for custom classes / data structures between client and server? Here I assume client to be mean browser