runtime: UseWindowsService doesn't work correctly with single file executables

Describe the bug

.UseWindowsService() sets the base path to AppContext.BaseDirectory which ends up being something like C:\Windows\Temp\.net\FileUploader\blc0j22k.v0p when using a single file exe and running as a service. This prevents the appsettings.json files from being loaded if they’re saved alongside the exe which I’ve been told is an acceptable deployment scenario.

To Reproduce

Steps to reproduce the behavior:

1. Using version 3.0.0-preview7.19362.4 of package Microsoft.Extensions.Hosting.WindowsServices
2. Create an appsettings.json with a setting in it
3. In .ConfigureServices(ctx, services) call ctx.Configuration.GetValue<string>("SomeValue")
4. Publish the project using dotnet publish --configuration Release --output artifacts /p:PublishSingleFile=true /p:PublishTrimmed=true
5. Install the service & run it
6. The value in appsettings.json will not be loaded

Expected behavior

The appsettings.json stored alongside the exe should be loaded when running a single file exe as a service.

Current workaround

I originally was using the following code before I added in the Microsoft.Extensions.Hosting.WindowsServices package which I got from the asp.net core 2.2 docs:

var isService = !(Debugger.IsAttached || args.Contains("--console"));

if (isService)
{
    using var process = Process.GetCurrentProcess();
    var pathToExe = process.MainModule.FileName;
    var pathToContentRoot = Path.GetDirectoryName(pathToExe);
    Directory.SetCurrentDirectory(pathToContentRoot);
}

After adding this package I modified the code like so:

 var builder = Host.CreateDefaultBuilder()
     .UseWindowsService()
     .ConfigureServices((ctx, services) =>
     {
     });
 
+if (WindowsServiceHelpers.IsWindowsService())
+{
+    using var process = Process.GetCurrentProcess();
+    var pathToExe = process.MainModule.FileName;
+    var pathToContentRoot = Path.GetDirectoryName(pathToExe);
+
+    builder.UseContentRoot(pathToContentRoot);
+}
 else
 {
     builder.UseConsoleLifetime();
 }
 
 var host = builder.Build();

Depending on how you publish the application this might not be a bug but rather a documentation note. It seems worth mentioning though.