struct sta­tic ini­tial­izer method apply to UDA

[learnfirst1 via Digitalmars-d-learn]

my question is how to easy use struct sta­tic ini­tial­izer 
method with UDA.

Fake code:
struct DbColumn {
         string name;
        bool    unique ;
        bool    signed ;
        bool    nullable ;
}

struct Order {
        uint id;
        
        @DbColumn({ .nullable= true}) // not working
        string order_id;

        @DbColumn({ :nullable= true}) // not working
        string order_time;

        @DbColumn(nullable= true) // not working
        string order_time;
}