code: func handleConfigMapFromEnvFileSource(configMap *v1.ConfigMap, envFileSource string) error {
  	info, err := os.Stat(envFileSource)
  	if err != nil {
  		switch err := err.(type) {
  		case *os.PathError:
  			return fmt.Errorf("error reading %s: %v", envFileSource, err.Err)
  		default:
  			return fmt.Errorf("error reading %s: %v", envFileSource, err)
  		}
  	}
  	if info.IsDir() {
  		return fmt.Errorf("env config file cannot be a directory")
  	}
  
  	return addFromEnvFile(envFileSource, func(key, value string) error {
  		return addKeyFromLiteralToConfigMap(configMap, key, value)
  	})
  }
docs: // handleConfigMapFromEnvFileSource adds the specified env file source information
  // into the provided configMap