Why only inserts one object in list and returns empty array

Im making a post and get request but only inserts one object int List and in the get request always returns a empty array []

using Microsoft.AspNetCore.Mvc;
using rest_api_crud.Models;

namespace rest_api_crud.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class UsersController : ControllerBase
    {
         List<UsersModel> users = new List<UsersModel>();//List of users

        [HttpPost(Name = "PostUser")]
        public List<UsersModel> Post()
        {
            users.Add(new UsersModel() { Name = "test", Age = 19 });// inserts only 1 new user to list
            return users;
        }

        [HttpGet(Name = "GetUsers")]
        public List<UsersModel> Get()
        {   
            return users; // returns empty array
        }
    }
}