How can i correctly handle SIGTERM signal Heroku via C#?

In a telegram bot written in c#, I use the following code to catch the bot shutting down(SIGTERM call):

using Mono.Unix;
using Mono.Unix.Native;
public class UnixExitSignal
{
    private event EventHandler OnExecute;
    private readonly UnixSignal[] signals = new UnixSignal[]{
    new UnixSignal(Signum.SIGTERM),
};
    public UnixExitSignal(EventHandler OnExecute)
    {
        this.OnExecute = OnExecute;
    }
    public void Wait()
    {
        _ = Task.Factory.StartNew(() =>
        {
            _ = UnixSignal.WaitAny(signals, -1);
            OnExecute(null, EventArgs.Empty);
        });
    }
}

After a certain amount of time I meet this error:

Conflict: terminated by other getUpdates request; make sure that only one bot instance is running

How can I correctly complete the task so as not to meet the above error in the future?