KeyedServiceProxy.cs

using Microsoft.Extensions.DependencyInjection;

public sealed class KeyedServiceProxy<T>
    where T : notnull
{
    private readonly IServiceProvider serviceProvider;

    public KeyedServiceProxy(IServiceProvider serviceProvider)
    {
        this.serviceProvider = serviceProvider;
    }

    public T Get(object key) => serviceProvider.GetRequiredKeyedService<T>(key);
}