code: func WrapErrorf(cause error, code ErrCode, format string, args ...interface{}) error {
  	if cause == nil {
  		return nil
  	}
  
  	return &Err{
  		Code:    code,
  		Message: fmt.Sprintf(format, args...),
  		Cause:   cause,
  	}
  }
docs: /*
  WrapErrorf returns an *Err that wraps another arbitrary error with an ErrCode and a message.
  
  If cause is nil, returns nil, so you can use it like
  	return util.WrapErrorf(DoSomethingDangerous(), util.NetworkError, "well that didn't work")
  
  If cause is known to be of type *Err, use WrapErrf.
  */