Question

an object experiences a net non-zero force is it possible for the object to move with a constant speed along a straight line

Answer 1

yes it is possible if there is no force acting opposite to the object and the speed of the object is not zero
example is an object roaming in space will never stop until some forces will act on it
because in space there is no resistance of atmosphere and if the object is not in the gravitational pull of any celestial body

Answer 2

Yes it is possible! Not practically but....