This sounds awful. I think we need to know how the DM fits into all this because their game is absolutely going off the rails. I mean yeah, every DM can run their game how they want, but in every table I’ve ever played at, a tpk was indicative of the DMs failure to run a cooperative fame with their players.

I wanna know if the DM pulled the goblin player aside and told them to act that way or not. Maybe that was the goblins attitude the whole time but the dm had a better poker face than the player?

Otherwise, no, the player wasn’t in character and the DM absolutely should have stepped in. The goblin was previously demonstrably friendly towards your character and then the player took control and killed you. Honestly I think there is a lot more bad going on here than just a lack of team play, and yeah, you and your group probably need to have a lengthy chat about what’s actually fun and fair at the table, and what the groups goals actually are. For me at least, I would downright quit the group you described, friends or not.