middleware.cs

// middleware.cs file
public class HydrateContextMiddleware
{
    private RequestDelegate _next;
    public HydrateContextMiddleware(RequestDelegate next)
    {
        _next = next;
    }
    public async Task Invoke(HttpContext context, IContextWriterService contextService)
    {
        contextService.Username = context.User.Identity.Name;
        await _next(context);
    }
}

// startup.cs Configure method
app.UseMiddleware<HydrateContextMiddleware>();