Call WebApplication.CreateBuilder(args) only once

Author: tdykstra

aspnetcore/fundamentals/configuration/index.md

@@ -59,6 +59,9 @@ var builder = WebApplication.CreateBuilder(args);
 1. [appsettings.json](#appsettingsjson) using the [JSON configuration provider](#jcp).
 1. A fallback to the host configuration described in the [next section](#host).
 
+> [!Important]
+> While this article mentions `WebApplication.CreateBuilder(args)` many times, application code should call this method only once. For more information, see [this IIS Support blog post](https://techcommunity.microsoft.com/blog/iis-support-blog/asp-net-core-503-server-has-been-shutdown/3830338)
+
 <a name="host"></a>
 
 ### Default host configuration sources