This is easy to accomplish when you're calling a function that only returns an error. You can do:

if err := whatever(); err != nil {
    return err
}

In the outer scope, err remains undefined, which is what I want. But when calling a function that returns a value as well as an error, this is the best I've been able to come up with:

var exe string
{
    var err error
    exe, err = os.Executable()
    if err != nil {
        return err
    }
}

You might ask, who cares if err winds up in the outer scope? You can just redeclare it with := over and over, and nothing bad happens. I completely agree, and that's what I do most of the time. I just don't like it, so I'm interested in whether anyone can come up with a more terse or elegant way to keep err out of the outer scope.