I kept the example simple, of course I could now customize the error message further (or take some other sensible action). Note that I returned a 400, not a generic 502 here. If I didn't care at all, I wouldn't need any extra lines. Does the panic handler send a response at all, or does it just drop the connection?

Also, in Go, using panic/recover is considered unidiomatic. You can use it like an exception system, but it's not what you're supposed to do.

I'm not suggesting that you would build a custom exception recovery system; I'm pointing out that net/http, which is definitionally idiomatic, already has that recovery mechanism.

I believe that that recovery mechanism isn't supposed to be routinely triggered just due to bad user input, and that code that does so would be considered defective.

It's doing almost literally the same thing as the Python code upthread. Just, with less code.

I think that was more of an example. There are lots of ways to fail gracefully when you don't have the data you want in the dict.

Right, which is why json.Unmarshal returns an error, and why map lookups return an extra `ok` value in Go.

It would be a lot more than 4 lines in Go though. Either the struct definition, or a lot of `if !ok return error`. Especially once the nesting gets deeper.

I'm pretty sure it would just be an `if err != nil {http.Error(w, err.Error(), 501); return }`.

one of these for each nesting level.