like a shot vs forthwith

like a shot and forthwith both are adverbs.

Word	Noun	Adjective	Verb	Adverb
like a shot	No	No	No	Yes
forthwith	No	No	No	Yes

As adverbs, like a shot and forthwith are synonyms defined as:

like a shot and forthwith: without delay or hesitation; with no time intervening

Other synonyms of like a shot include at once, directly, immediately, instantly, now, right away, straight off, straightaway.

like a shot (adverb)	forthwith (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening