private async Task CargarPublicaciones()
        {
            HttpClient client = new HttpClient();

            client.BaseAddress = new Uri("192.168.1.59");

            //se debe declarar el metodo async
            var request = await client.GetAsync("/api/Publicaciones");

            if (request.IsSuccessStatusCode)
            {
                var responseJson = await request.Content.ReadAsStringAsync();

                var response = JsonConvert.DeserealizeObject <List <Publicacion> >(responseJson);
                listPublicacion.ItemSource = response;
            }
        }