code: func (c *CustomerIO) Identify(customerID string, attributes map[string]interface{}) error {
  	j, err := json.Marshal(attributes)
  
  	if err != nil {
  		return err
  	}
  
  	status, responseBody, err := c.request("PUT", c.customerURL(customerID), j)
  
  	if err != nil {
  		return err
  	} else if status != 200 {
  		return &CustomerIOError{status, c.customerURL(customerID), responseBody}
  	}
  
  	return nil
  }
docs: // Identify identifies a customer and sets their attributes