1000 years survival

After some time after the earth was at piece, son goku would spend his years alone on earth after seeing his 3rd generation decendance but didn't meet the requirements to replace goku as they all died by further powerful enemies. goku trained and fought for 1000 years as he remains on a wasted planet earth as all life were all gone and this s no bother to goku because he achieved immortality after becoming half dragon in the dragon realm and even if he can live for eternity, he could not protect earth forever