code: func (c *ConfigFile) MustInt(section, key string, defaultVal ...int) int {
  	value, err := c.Int(section, key)
  	if len(defaultVal) > 0 && err != nil {
  		return defaultVal[0]
  	}
  	return value
  }
docs: // MustInt always returns value without error,
  // it returns 0 if error occurs.