防止为空（或数据库中的空字符串值）

I'm using PostgreSQL and GORM in my Go app.

I thought that using the sql tab of sql:"not null" would do the trick of preventing a null entry, but when go initializes structs with a string type then it defaults to an empty string which is not the same as null in the db.

I am wondering if there is a way to prevent this from happening in a struct definition so I wouldn't have to strictly enforce it at all levels in the application code.