code: func (m MapClaims) VerifyNotBefore(cmp int64, req bool) bool {
  	switch nbf := m["nbf"].(type) {
  	case float64:
  		return verifyNbf(int64(nbf), cmp, req)
  	case json.Number:
  		v, _ := nbf.Int64()
  		return verifyNbf(v, cmp, req)
  	}
  	return req == false
  }
docs: // Compares the nbf claim against cmp.
  // If required is false, this method will return true if the value matches or is unset