Program.cs

using Fusonic.GitBackup;
using Fusonic.GitBackup.Models;
using Fusonic.GitBackup.Services;
using MailKit.Net.Smtp;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using SimpleInjector;
using SimpleInjector.Lifestyles;

Container container = null;

try
{
    container = Bootstrapper.CreateContainer();
    using (AsyncScopedLifestyle.BeginScope(container))
    {
        await container.GetService<App>().Run();
    }
}
catch (Exception ex) when (container != null)
{
    var sentMail = SendErrorMail(ex);
    using (AsyncScopedLifestyle.BeginScope(container))
    {
        var logger = container.GetService<ILogger>();
        if (sentMail)
        {
            logger.LogError("An error occured. An email with detailed error message has been sent to the address defined in the app-settings.json.");
        }
        logger.LogError(ex.ToString());
    }
}

bool SendErrorMail(Exception ex)
{
    using (AsyncScopedLifestyle.BeginScope(container))
    {
        var settings = container.GetService<AppSettings>();
        if (string.IsNullOrEmpty(settings.Mail.Host))
            return false;

        using var client = new SmtpClient();
        client.Connect(settings.Mail.Host, settings.Mail.Port, settings.Mail.UseSsl);
        client.Authenticate(settings.Mail.Username, settings.Mail.Password);

        var mailClient = new MailClient(settings, client);
        mailClient.SendMail("Git-Backup Fatal Error!", ex.ToString());
        return true;
    }
}