Spoilers ahead for Captain Marvel. In addition to welcoming Carol Danvers (Brie Larson) to the MCU, Captain Marvel brought us the instantly irreplaceable Goose — an alien being called a Flerken masquerading as a tabby cat. As you know if you stayed for the post-credits scene, Goose eventually coughs the Tesseract up like a hairball onto Nick Fury's (Samuel L. Jackson) desk. It's unclear when exactly that happens in the chronological timeline, but it could help shed light on where Goose has been since Captain Marvel.
As Vox pointed out, Fury's desk in the second post-credits scene looks different from the one we see during the man action of Captain Marvel. Notably, the post-credits version doesn't have anything on it, which suggests that Fury no longer uses that desk and at least some time has passed since 1995, when Captain Marvel takes place. (His computer is different too.) That means that Goose is around on earth after Captain Marvel. In fact, he's most likely on earth at the end of the movie too, when Carol flies off to space to discover the rest of the universe with her newly mastered superpowers.
In Marvel comics, though, the comic book equivalent of Goose, a Flerken cat named Chewy, accompanies Carol on her various astral excursions.
Now, you can fill in some of the blanks in the Tesseract's timeline following Captain Marvel thanks to its important role in The Avengers. In the 2012 first team-up film, the Tesseract is kept in a lab belonging to Project P.E.G.A.S.U.S., which Goose's previous owner, Mar-Vell (Annette Bening), had presided over before her death. Once Goose swallowed the Tesseract and held it inside its mouth — which, being a Flerken and all, has many pockets, including some that lead to other dimensions — the Tesseract was placed in S.H.I.E.L.D.'s possession, where it was likely kept until The Avengers, since S.H.I.E.L.D. collaborated with NASA and the Air Force on Project P.E.G.A.S.U.S., per Marvel's Wiki.
That only leaves the question of when in the timeline the post-credits scene with Goose takes place. The desk where the Flerken coughed up the Tesseract has been cleared, likely after Fury became Director of S.H.I.E.L.D. and upgraded to a new desk. The scene itself could imply that Goose somehow got ahold of the Tesseract after sticking around on earth with Fury — despite their strained relationship — but it also could hint that, maybe, Goose accompanied Captain Marvel on a mission to steal back the Tesseract, Loki-style, perhaps to help save the earth from Thanos.
Whenever it's set, the clip could reveal a possible avenue for Captain Marvel helping the Avengers in Endgame. After all, the Flerken's ability to hold alternate dimensions in its mouth could come in handy when the Avengers need to find the Infinity Stones following Thanos' snap of death at the end of Infinity War.
Even if we can't pinpoint exactly where Goose is at all times between Captain Marvel and Endgame, we can at least presume that Goose doesn't die in the meantime. Marvel Studios head Kevin Feige hinted that Goose is probably still alive, 20+ years after the events from Captain Marvel. "A Flerken might be longer lived [than a cat]," Feige told SlashFilm, then added, "Is Goose out there? She could be."
It sounds like the chances of Goose returning to the MCU either in Endgame or afterwards are pretty good. Until then, you just have to imagine the orange kitty who's quick to turn on you following Captain Marvel around on her many space adventures.
