Well, it seems that they've just chosen the second option (no pun intended) that I've mentioned above - that is, to define a monad to abstract this. There may be some benefit to doing this instead of pointers, but as you've found yourself, using a monad requires you to pass that monadic type up the calling chain (OR to unwrap that and deal with both cases safely).

I haven't used SQL databases with Go much, so I'm just looking at NullFoo types now for the first time, but every time I've thought I could improve on the design of Go in some way, the folks on #go-nuts have (kindly) shown me that I wasn't really thinking about things the right way. So, there's probably some reason that it's been designed this way, but I'm saying that purely based on prior experience with other Go matters, not with package "database/sql".