diplomat vs go-between

diplomat and go-between both are nouns.

Word	Noun	Adjective	Verb	Adverb
diplomat	Yes	No	No	No
go-between	Yes	No	No	No

As nouns, go-between is a hypernym of diplomat; that is, go-between is a word with a broader meaning than diplomat:

Other hypernyms of diplomat include intercessor, intermediary, intermediator, mediator.

diplomat (noun)	go-between (noun)
an official engaged in international negotiations	a negotiator who acts as a link between parties
a person who deals tactfully with others