[nishs]

The last case is rarely seen in Go (at least not in the standard library).

Accepting for the moment that Go has no exceptions and and error returns are the way to go, the first two cases make sense.

The third case ( value, error) is actually useful in several scenarios. For instance, considering you're writing bytes to a stream that fail partway. The value is the number of bytes return so far and the error is the error that was encountered. In fact, this is the signature that the ubiquitous io.Writer's Write method uses.

If all you had was single return values (aka "int or throw Exception"), how would you model the io.Writer?

[simon_o]

> If all you had was single return values (aka "int or throw Exception"), how would you model the io.Writer?

This is not an problem, because a single return value is _not_ everything one has.