How to send a json as a response when you have a 401 error that occurs due to being unauthorized (JWT)

Question

I am new to C#. I have a project using C#, ASP.NET Core 3.1 and Entity Framework.

I have done all the JWT configuration.

    [Authorize(AuthenticationSchemes = JwtBearerDefaults.AuthenticationScheme)]
    [HttpPost, Route("delete/{id}")]
    public async Task<ActionResult<Login>> DeleteUsuario(int id)
    .
    .
    .

in Startup.cs

      public void ConfigureServices(IServiceCollection services){
        services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
        .
        .

  public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
  {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();
        app.UseRouting();
        app.UseAuthorization();
        app.UseAuthentication();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
}

When the token is not sent immediately as a response a 401 error is generated. I would like to return a json like this, when I getting this error:

{"message": "Sign in"}

How can I do it?