public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory, IApplicationLifetime appLifetime, IRequestContext requestContext)
        {
           loggerFactory.AddSerilog();

           // Ensure any buffered events are sent at shutdown
            appLifetime.ApplicationStopped.Register(Log.CloseAndFlush);

            var logger = loggerFactory.CreateLogger<Startup>();

            app.UseExceptionHandler(
                options =>
                {
                    options.Run(
                        async context =>
                        {
                            context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
                            var ex = context.Features.Get<IExceptionHandlerFeature>();
                            if (ex != null)
                            {
                                var errmsg = "An unexpected error has occured in API.";
                                var logDetails = new
                                {
                                    CorrelationId = requestContext.CorrelationId,
                                    Message = errmsg
                                };
                                logger.LogError(1001, ex.Error, "{@LogDetails}", logDetails);
                                await context.Response.WriteAsync(errmsg).ConfigureAwait(false);
                            }
                        });
                });

            app.UseMvc();

            logger.LogInformation("Application has started in environment {0}", env.EnvironmentName);
        }