Named connection string was not found in application configuration

Question

I added a Startup.cs to my .NET 6 console application as described here. To avoid having to manually specify the connection string when calling Scaffold-DbContext, I tried to provide the connection string from the application configuration like this:

Scaffold-DbContext -Connection name=DatabaseConnectionName -Provider...

For some reason, this does not seem to work and I get the following error:

System.InvalidOperationException: A named connection string was used, but the name 'DatabaseConnectionName' was not found in the application's configuration. Note that named connection strings are only supported when using 'IConfiguration' and a service provider, such as in a typical ASP.NET Core application. See https://go.microsoft.com/fwlink/?linkid=850912 for more information.

Here is the content of my Startup.cs:

public class Startup
{
    IConfiguration Configuration { get; }

    public Startup()
    {
        IConfigurationBuilder builder = new ConfigurationBuilder()
            .AddJsonFile("appsettings.json");

        Configuration = builder.Build();
    }
    
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddEntityFrameworkNpgsql().AddDbContext<DatabaseContext>(opt =>
            opt.UseNpgsql(Configuration.GetConnectionString("DatabaseConnectionName")));

        services.AddSingleton(Configuration);
    }
}

And this is the content of my appsettings.json:

{
  "ConnectionStrings": {
    "DatabaseConnectionName": "User ID=...;Password=...;Server=...;Port=5432;Database=database-name;Integrated Security=true;Pooling=true"
  }
}

I noticed that this error only occurs while trying to execute the Scaffold-DbContext command, but not when I am running the application normally. I think that this problem might be related to the fact that I am manually creating an instance of the Startup class in my Program.cs, but I don't know if that is true or what I can do about this.

Is there any way how I can fix this error and let the command read the connection string from the configuration file?