drivers/azure/azureutil/auth.go
func mkTokenCallback(path string) azure.TokenRefreshCallback {
	return func(t azure.Token) error {
		if err := azure.SaveToken(path, 0600, t); err != nil {
			return err
		}
		log.Debug("Saved token to file.")
		return nil
	}
}
func mkTokenCallback(path string) azure.TokenRefreshCallback {
	return func(t azure.Token) error {
		if err := azure.SaveToken(path, 0600, t); err != nil {
			return err
		}
		log.Debug("Saved token to file.")
		return nil
	}
}
// mkTokenCallback returns a callback function that can be used to save the
// token initially or register to the Azure SDK to be called when the token is
// refreshed.