0 is an untyped constant whose default type is
uint64, and when doing comparison with an interface, the thing you are comparing to must be both the same type and the same value for them to be considered equal.
The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows:
A value x of non-interface type X and a value t of interface type T are comparable when values of type X are comparable and X implements T. They are equal if t's dynamic type is identical to X and t's dynamic value is equal to x.