code: func (s *Adaptor) ServoWrite(pin string, angle byte) (err error) {
  	if _, present := s.servoPins[pin]; !present {
  		err = s.servoPinOpen(pin)
  		if err != nil {
  			return
  		}
  	}
  
  	params := url.Values{
  		"params":       {fmt.Sprintf("%v,%v", pin, angle)},
  		"access_token": {s.AccessToken},
  	}
  	url := fmt.Sprintf("%v/servoSet", s.deviceURL())
  	_, err = s.request("POST", url, params)
  	return err
  }
docs: // ServoWrite writes the 0-180 degree angle to the specified pin.
  // To use it requires installing the "tinker-servo" sketch on your
  // Particle device. not just the default "tinker".