code: func Copy(dst interface{}, src interface{}) error {
  	if dst == nil {
  		return fmt.Errorf("dst cannot be nil")
  	}
  	if src == nil {
  		return fmt.Errorf("src cannot be nil")
  	}
  	bytes, err := json.Marshal(src)
  	if err != nil {
  		return fmt.Errorf("Unable to marshal src: %s", err)
  	}
  	err = json.Unmarshal(bytes, dst)
  	if err != nil {
  		return fmt.Errorf("Unable to unmarshal into dst: %s", err)
  	}
  	return nil
  }
docs: // Make a deep copy from src into dst.