ignore the flag when its name is - or the field is un-exported
for example:
type config {
Start string `name:"start" desc:"in the format of 2006-01-02T15:04:05"`
StartTime time.Time `name:"-"` // won't be shown in the flag list
Stop string `name:"stop" desc:"in the format of 2006-01-02T15:04:05"`
stopTime time.Time // won't be shown in the flag list
}