We see this all the time in the gym and people struggle with improper form as they feel it is the best way to work their traps and upper back. Unless you have very flexible shoulders, this exercise is difficult to do correctly, and can increase your risk for shoulder impingement syndrome (a painful condition in which the muscles or tendons of your rotator cuff become entrapped in your shoulder joint). Not only that, but the tendency is to hit the back of the neck with the bar which could injure the cervical vertebrae. Please avoid this exercise.
The proper technique is to just pull the bar in front of your head, down to your collarbone. You’ll work your back just as hard, but with less risk for injury.