code: func (r *Request) ParamDuration(name string) *time.Duration {
  	v, set := r.Req.URL.Query()[name]
  	if !set {
  		return nil
  	}
  
  	d, err := time.ParseDuration(v[0])
  	if err != nil {
  		return nil
  	}
  	return &d
  }
docs: // ParamDuration parses a duration string, example: "1m30s"
  // that will be 1 minute and 30 seconds