Solution3Scan.cs

public void ConfigureServices(IServiceCollection services)
{
    ...
    services.Scan(i =>
        i.FromCallingAssembly()
        .InjectableAttributes()
    );

    /* Or */
    services.Scan(i =>
        i.FromCallingAssembly()
        .InjectableAttribute(ServiceLifetime.Transient)
        .InjectableAttribute(ServiceLifetime.Scoped)
        .InjectableAttribute(ServiceLifetime.Singleton)
    );
    ...
}