have a go vs attempt

have a go is not a noun while attempt is a noun.

Word	Noun	Adjective	Verb	Adverb
have a go	No	No	Yes	No
attempt	Yes	No	Yes	No

As verbs, attempt is a hypernym of have a go; that is, attempt is a word with a broader meaning than have a go:

Other hypernyms of have a go include assay, essay, seek, try.

have a go (noun)	attempt (noun)
	earnest and conscientious activity intended to do or accomplish something
	the act of attacking

have a go (verb)	attempt (verb)
make an attempt at something	enter upon an activity or enterprise
	make an effort or attempt