code: func (c *cachedLoader) MustGetDuration(key string) time.Duration {
  	s := c.MustGetString(key)
  	ret, err := time.ParseDuration(s)
  	if err != nil {
  		panic(fmt.Sprintf("Could not parse config (%s) into a duration: %v", key, err))
  	}
  	return ret
  }
docs: // MustGetDuration fetches the config and parses it into a duration.  Panics on failure.