Problems accessing a web api in a Xamarin Forms project

Question

On my first screen of mine app mobile what I’m doing is the screen of Login, but whenever I try to log the return is

Statuscode: 404,

Reasonphrase: 'Not Found'

I have confirmed and the uri is correct, access via Postman normally, I began to suspect that it is something lacking to configure in the project or manifest of app, I already tested the project Android and UWP, all give the same problem.

What gave me this certainty is that I created a console app just to test access to api, everything works normally, follows the code:

using Newtonsoft.Json.Linq;
using System.Collections.Generic;
using System.Net.Http;

namespace app1
{
    class Program
    {
        static void Main(string[] args)
        {
            var url = "https://api.dominio.com.br/login";
            var userName = "[email protected]";
            var password = "12345678";

            var token = GetToken(url, userName, password);
        }

        static string GetToken(string url, string userName, string password)
        {
            var pairs = new List<KeyValuePair<string, string>>
                    {
                        new KeyValuePair<string, string>( "username", userName ),
                        new KeyValuePair<string, string> ( "password", password )
                    };
            var content = new FormUrlEncodedContent(pairs);
            
            using (var client = new HttpClient())
            {
                var response = client.PostAsync(url, content).Result;
                JObject o = JObject.Parse(response.Content.ReadAsStringAsync().Result);
                return (string)o["token"];
            }
        }
    }
}

How can I solve this problem ?

On request I will put the code that is not working, although it is the same as the code above:

using Newtonsoft.Json.Linq;
using System.Collections.Generic;
using System.Net.Http;
using System.Threading.Tasks;

namespace AppMobile.Services
{
    public class Auth : IAuthenticate
    {
        const string Url = "https://api.dominio.com.br/Login";
        
        public async Task<string> GetToken(string user, string pass)
        {
            var pairs = new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>( "username", user ),
                new KeyValuePair<string, string> ( "password", pass )
            };
            var content = new FormUrlEncodedContent(pairs);
            using (var client = new HttpClient())
            {
                var response = await client.PostAsync(Url, content);
                JObject obj = JObject.Parse(response.Content.ReadAsStringAsync().Result);
                var token = (string)obj["token"];
                
                return token;
            }
        }
    }
}

Answer 1

I was able to resolve by changing the post to not run asynchronously:

var response = await client.PostAsync(Url, content).ConfigureAwait(false);

So it worked in the console application, there it was synchronous. I haven’t found anything in the documentation that explains why this should work asynchronously...