I say this not to defend Go, but to encourage anyone creating a JSON-based API to at least test with a statically-typed language. It's too easy in a dynamically-typed language to create a field that is either a number or a list of numbers, but you just boned all the static languages in the process. Unless you know you're only talking internally, and you're never going to change to a static language of any kind, JSON APIs should generally be written in a subset of JSON that is static-friendly.

It's not that crazy of a requirement anyhow; it's not really a great plan in dynamic languages either because it complexifies the code there, too, just not as much. It's a bit of discipline, yeah, but it's good for you even in a purely-dynamic environment.