SigIntTerm.cs

using System;
using System.Threading.Tasks;

var tcs = new TaskCompletionSource();
var sigintReceived = false;

Console.WriteLine("Waiting for SIGINT/SIGTERM");

Console.CancelKeyPress += (_, ea) =>
{
    // Tell .NET to not terminate the process
    ea.Cancel = true;

    Console.WriteLine("Received SIGINT (Ctrl+C)");
    tcs.SetResult();
    sigintReceived = true;
};

AppDomain.CurrentDomain.ProcessExit += (_, _) =>
{
    if (!sigintReceived)
    {
        Console.WriteLine("Received SIGTERM");
        tcs.SetResult();
    }
    else
    {
        Console.WriteLine("Received SIGTERM, ignoring it because already processed SIGINT");
    }
};

await tcs.Task;
Console.WriteLine("Good bye");