SeqInt() access to context obj about factory-go

[utx0]

Worked out a away to do what I needed:

var (
	seq         int64 = 0
	zoneFactory       = factory.NewFactory(&Zone{}).Attr("Name", func(args factory.Args) (interface{}, error) {
		region_name := args.Context().Value("region_name").(string)
		new := atomic.AddInt64(&seq, 1)
		return fmt.Sprintf("%v-%v", region_name, zone(int(new))), nil
	})
)