[blcknight]

> If the work you do after the defer has other side effects

Defer is by definition the last work you do in a function, there won't be more work except by the caller who will get the error returned to them.

If you are structuring a function that writes a file, and then does something with it, defer isn't appropriate, since you should close it before you do any more work.

[Cthulhu_]

It's possible to have multiple defers in a function though (so you have multiple "last work in a function"; nowhere is it dictated that a function should only have one operation that needs to clean something up at the end. Think for example copying one file to another.