> To avoid encountering this issue, return `error`, not something else.

But best practice is to return concrete types.

Also, `err` is just an example in this minimal snippet. It can happen with any variable.

Here's a similar snippet: https://play.golang.org/p/WKPey_PL_ht -- Looks impossible to crash. :P

Spoiler: it's a boxed null, not a null.