Away and At once

Away adverb - From this or that place.

At once and away are semantically related In some cases you can use "At once" instead an adverb "Away".

At once adverb - Without delay or hesitation; with no time intervening.

Away and at once are semantically related in immediately topic. Sometimes you can use "Away" instead an adverb phrase "At once", if it concerns topics such as directly, presently, right now.