some "nullable" base types for go

nullables.go

type NullableString string

func (n NullableString) MarshalJSON() ([]byte, error) {
        sn := string(n)
        if sn == "" {
                var i interface{}
                return json.Marshal(i)
        }
        return json.Marshal(sn)
}

type NullableUInt64 uint64

func (n NullableUInt64) MarshalJSON() ([]byte, error) {
        in := uint64(n)
        if in == 0 {
                var i interface{}
                return json.Marshal(i)
        }
        return json.Marshal(in)
}