I've no idea how many times this question has been asked... same answer each time... supposing the hole went exactly through the center, one would accelerate at g = 9.8 m/s^2 (surface gravity) but your weight would lessen as you approached the center of the Earth, becoming zero at that point. This doesn't take into account any air resistance.
The person's speed, however would be near 17,700 mph, taking only 42 minutes or so for the entire trip (from one side to the other) before he would slow and reach the opposite lip of the hole... If nothing interfered, the person would fall back into the hole, accelerating again and reaching the lip on the other side... the entire round trip taking about 85 minutes... ad infinitum...
This doesn't consider if the hole was drilled from pole to pole or from a point on the equator to another like point...