how to add idAttribute in migration file

CLI version 3.1.2, Titanium SDK version 3.1.2.GA , Alloy 1.2.0

I have tried doing

db.idAttribute ="gID";

migration.up = function(db) {
    db.dropTable();
 
    db.createTable({
        columns : {
            "fnName" : "TEXT",
            "gID" : "INTEGER PRIMARY KEY AUTOINCREMENT"
        },
        adapter : {
            "idAttribute" : "gID"
        },
    });
 
};
 
migration.down = function(db) {
 
};