code: func (c *ConfigFile) MustValue(section, key string, defaultVal ...string) string {
  	val, err := c.GetValue(section, key)
  	if len(defaultVal) > 0 && (err != nil || len(val) == 0) {
  		return defaultVal[0]
  	}
  	return val
  }
docs: // MustValue always returns value without error.
  // It returns empty string if error occurs, or the default value if given.