Be as good as gone phrase
Be very nearly or inevitably lost, departed or deceased
He is in terminal cancer so I’m afraid he is as good as gone.
His job is as good as gone for a hate tweet.
To cause damages, bad effects, or even deaths to somebody or something
Lost among a confusing mix of things
To indicate one is lost in deep thought or concentration and does not aware of what is happening around him/her
To disappear.
The verb "be" should be conjugated according to its tense.
If someone has a cast iron stomach, they have a strong stomach that can digest unusual food and even bad food without being ill.
Jimmy must have a cast-iron stomach, when he drank milk with lime juice and felt perfectly fine afterward.