call_opt.go
func PickID(id ID) CallOption {
	return callOptionFunc(func(r *Request) error {
		r.ID = id
		return nil
	})
}
func PickID(id ID) CallOption {
	return callOptionFunc(func(r *Request) error {
		r.ID = id
		return nil
	})
}
// PickID returns a call option which sets the ID on a request. Care must be
// taken to ensure there are no conflicts with any previously picked ID, nor
// with the default sequence ID.