It depends. In this trivial case, what do you do if you find s == nil is true? You probably panic anyway. Unless you have some specific reason to panic with a different message to the default “nil pointer dereference” then there’s no point checking it.
The point is that you should check for null, then be able to represent the variable as something that can't be null.
That way once you've checked it's not null (somewhere you're not forced to panic ideally), you can pass around the pointer & be confident you don't need to ever check it again.
