code: func (o *OrderService) UpdateForCSR(orderURL string, csr []byte) (acme.Order, error) {
  	csrMsg := acme.CSRMessage{
  		Csr: base64.RawURLEncoding.EncodeToString(csr),
  	}
  
  	var order acme.Order
  	_, err := o.core.post(orderURL, csrMsg, &order)
  	if err != nil {
  		return acme.Order{}, err
  	}
  
  	if order.Status == acme.StatusInvalid {
  		return acme.Order{}, order.Error
  	}
  
  	return order, nil
  }
docs: // UpdateForCSR Updates an order for a CSR.