Green’s Dictionary of Slang

an excl. used to indicate that something is very good.

1988		S. King Tommyknockers (1989) 232: But look! Neat-o, huh? Awesome!
1999		K. Sampson Powder 400: Awesome, guys! Totally awesome!
2009		D. Gram Lost City of Z 68: He asked how long I intended to go, and I said I didn’t know—at least a month, probably more. ‘Awesome. Awesome. That should let you get immersed in the place’.
2018		G. Gilmore Class Act [ebook] [H]e was a good-enough kid, amazed by everything he was told (‘Awesome!’).