(idiomatic) To seek short term gain at the sacrifice of long term profit.
Origin of kill-the-goose-that-lays-the-golden-eggs
From the Aesop's fable The Goose that Laid the Golden Eggs, in which a married couple own a goose that lays one golden egg every day. For greed, they decide to kill the goose to obtain all the gold they suppose to be inside. Once opened, the goose proves to be like any normal goose inside.