code: func Open(driverName, auth string) (*Conn, error) {
  	driversMu.RLock()
  	driveri, ok := drivers[driverName]
  	driversMu.RUnlock()
  	if !ok {
  		return nil, fmt.Errorf("sms: unknown driver %q (forgotten import?)",
  			driverName)
  	}
  	conn, err := driveri.Open(auth)
  	if err != nil {
  		return nil, err
  	}
  	c := &Conn{
  		driver: driveri,
  		conn:   conn,
  	}
  	return c, nil
  }
docs: // Open a connection to a registered driver.