What is the meaning of -다고?

Used other than figuratively or idiomatically: see (-da), (-go).

Used for the indirect quotation of sentences in the declarative.

In the intimate style, used to express relief that something has not come to pass.

Used to note that someone is using something as a reason or excuse, sometimes with a pejorative nuance.

Used to cite proverbs, maxims, and aphorisms.

Source: wiktionary.org