// in startup
app.UseMiddleware(typeof(ErrorHandlingMiddleware));

public class ErrorHandlingMiddleware
    {
        private readonly RequestDelegate next;

        public ErrorHandlingMiddleware(RequestDelegate next)
        {
            this.next = next;

        }

        public async Task Invoke(HttpContext context)
        {
            try
            {
                await next(context);
            }
            catch (Exception ex)
            {
                await HandleExceptionAsync(context, ex);
            }
        }

        private async Task HandleExceptionAsync(HttpContext context, Exception exception)
        {
            var code = HttpStatusCode.InternalServerError;

            var result = JsonConvert.SerializeObject(new { error = exception.Message });
            context.Response.ContentType = "application/json";
            context.Response.StatusCode = (int)code;
            await context.Response.WriteAsync(result);

        }
    }