Yes, GOALPOST is a Scrabble word!

Letter values in Scrabble US: G 2, O 1, A 1, L 1, P 3, O 1, S 1, T 1.

Is it a valid word?

GOALPOST is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

one of a pair of posts (usually joined by a crossbar) that are set up as a goal at each end of a playing field