SchemaMiddleware.cs

 public class SchemaMiddleware
    {
        private readonly RequestDelegate _next;

        public SchemaMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext context, OrdersSchema schema)
        {
            using (var printer = new SchemaPrinter(schema))
            {
                context.Response.ContentType = "application/text";
                context.Response.StatusCode = (int)HttpStatusCode.OK;

                await context.Response.WriteAsync(printer.Print());

                return;
            }
        }
    }