When Goldvein Hydra dies, it and Enduring Renewal trigger.
Resolve the Enduring Renewal trigger, returning Goldvein Hydra from your graveyard to your hand.
Resolve the Goldvein Hydra trigger, creating a tapped Treasure token.
When the token enters the battlefield, Amulet of Vigor triggers, untapping it.
Activate the Treasure by tapping and sacrificing it, adding ({G} magic symbol) .
Repeat.
Notes
Once you have infinite colorless mana, you may cast Goldvein Hydra with X equaling an arbitrarily large number, and then kill it to get infinite tapped Treasure tokens.