The pilot was taking his private pilot checkride, and was demonstrating a short field landing. During the landing the wind was gusty and he decided to go around. During the go-around, the left wing dropped and struck the runway. The Designated Pilot Examiner (DPE) took control of the airplane and completed the go-around. He then returned control of the airplane to the pilot, and the pilot then performed another short field landing with a full stop. After the full stop landing, he taxied to the fixed base operator (FBO) at the airport, and he and the DPE exited the aircraft and went into the FBO to complete the paperwork for the check ride. After the DPE had completed the paperwork, the pilot returned to the airplane with the intent to fly back to his home airport. During his preflight inspection he noticed that the wing was damaged. Examination of the damage by a Federal Aviation Administration inspector revealed that both wing spars were substantially damaged.