Arguably the most common line of code in Go, ‘if err != nil’ is doing what you’re saying you should never do in the language: check if an interface value is nil

Arguably the most common line of code in Go, ‘if err != nil’ is doing what you’re saying you should never do in the language: check if an interface value is nil. (And, in fact, care must be taken when returning custom error types precisely because of the typed nil issue.) So I don’t think the authors of the language see it the same way you do. (FWIW I was also a Go style reviewer working with the Go team for a few years, and I’ve never heard this idea from them in that time.)