当我们用另一个结构包装时，Gorm golang sql.NullInt64无法正常工作

In Go when you declare a type as an alias of another type, the new type does not get to keep the other type's methods. So here:

type NullInt64 sql.NullInt64

NullInt64sql.NullInt64

sql.NullInt64

type NullInt64 struct {
    sql.NullInt64
}