Plenty of German soldiers, along with foreign fighters who were forced to fight alongside them, did just that, once they knew the war was lost. Those German soldiers took an oath to Hitler, not the country, to fight to the death. Many of them violated that oath, because they knew the futility of dying for a lost cause.
That’s the only option.
Just tell Russia that you were forced to fight and you’ve chosen to not fight. You will not resist them and ask for mercy.