interact with Ratificacion/Login in https://apiadv.sintia.com.ar/Help/Api/POST-Ratificacion-Login

func login(url string, username string, password string) map[string]interface{} {
  values := map[string]string{"Usuario": username, "Clave": password}

  jsonValue, _ := json.Marshal(values)

  response, err := http.Post(url, "application/json", bytes.NewBuffer(jsonValue))
  if err != nil {
    panic(err)
  }
  defer response.Body.Close()

  bodyBytes, err := ioutil.ReadAll(response.Body)
  if err != nil {
    panic(err)
  }
  bodyString := string(bodyBytes)
  fmt.Println(bodyString)

  var result map[string]interface{}
  json.Unmarshal(bodyBytes, &result)

  return result
}