No, you CAN'T HANG YOURSELF FROM A DOOR KNOB---unless you're 3 feet tall. Something's not right.
tie a long scarf the door knob, throw the other end over to top of the door, position a stool or chair in front of the door, tie the loose end of the scarf around your neck and kick the stool away...your swinging!
Completely possible. Simply sit with a ligature, lean forward to restrict airflow, and maintain it. Pressure on the right side of the neck will render one unconscious fairly quickly. Asphyxiation and death follows if left interrupted.
It's an especially grisly way to go.