Update the Worker template to use Host.CreateApplicationBuilder (do…

…tnet#47720)

* Update the Worker template to use  `Host.CreateApplicationBuilder`

The callback approach that `Host.CreateDefaultBuilder` uses is no longer recommended going forward, and the programming model is no longer used in ASP.NET apps - it uses the `WebApplication.CreateBuilder()` API which is imperative, top-to-bottom programming. The Worker template should follow the same pattern.

Fix dotnet#43113

* Use var to fit in with ASP.NET.

src/ProjectTemplates/Web.ProjectTemplates/content/Worker-CSharp/Program.Main.cs

@@ -4,13 +4,10 @@ public class Program
 {
     public static void Main(string[] args)
     {
-        IHost host = Host.CreateDefaultBuilder(args)
-            .ConfigureServices(services =>
-            {
-                services.AddHostedService<Worker>();
-            })
-            .Build();
+        var builder = Host.CreateApplicationBuilder(args);
+        builder.Services.AddHostedService<Worker>();
 
+        var host = builder.Build();
         host.Run();
     }
 }

src/ProjectTemplates/Web.ProjectTemplates/content/Worker-CSharp/Program.cs

@@ -1,10 +1,7 @@
 using Company.Application1;
 
-IHost host = Host.CreateDefaultBuilder(args)
-    .ConfigureServices(services =>
-    {
-        services.AddHostedService<Worker>();
-    })
-    .Build();
+var builder = Host.CreateApplicationBuilder(args);
+builder.Services.AddHostedService<Worker>();
 
+var host = builder.Build();
 host.Run();

src/ProjectTemplates/Web.ProjectTemplates/content/Worker-FSharp/Program.fs

@@ -8,13 +8,12 @@ open Microsoft.Extensions.DependencyInjection
 open Microsoft.Extensions.Hosting
 
 module Program =
-    let createHostBuilder args =
-        Host.CreateDefaultBuilder(args)
-            .ConfigureServices(fun hostContext services ->
-                services.AddHostedService<Worker>() |> ignore)
 
     [<EntryPoint>]
     let main args =
-        createHostBuilder(args).Build().Run()
+        let builder = Host.CreateApplicationBuilder(args)
+        builder.Services.AddHostedService<Worker>() |> ignore
+
+        builder.Build().Run()
 
         0 // exit code