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