What was the main goal of Lincoln and the northerners?

abolition

restore unity

secession

ending slavery

At first, the goal of the civil war was to keep unity through the US, but under the worry that a European nation would get involved (Specifically Britain, since they would surround them) Lincoln announced that if the war was won, they would free the slaves

Lincoln did not assume the presidency or enter the Civil War with the intention of ending slavery in states where it already existed. Rather, his stated goal was to save the Union.