code: func (d *Device) AdvertiseServiceData16(ctx context.Context, id uint16, b []byte) error {
  	l := len(b)
  	prefix := []byte{
  		0x03, 0x03, uint8(id), uint8(id >> 8),
  		byte(l + 3), 0x16, uint8(id), uint8(id >> 8),
  	}
  	if err := d.sendReq(d.pm, 8, xpc.Dict{
  		"kCBAdvDataAppleMfgData": append(prefix, b...),
  	}).err(); err != nil {
  		return errors.Wrap(err, "can't advertise")
  	}
  	<-ctx.Done()
  	return ctx.Err()
  }
docs: // AdvertiseServiceData16 advertises data associated with a 16bit service uuid