A C177 pilot encountered windshear in IMC at 1;000' on an IFR approach and recovered at 700'.

Narrative

I filed an IFR flight plan with a Briefer for a flight to my home base. Conditions were IMC the entire route with light rain and very little turbulence. I asked Approach for the GPS RWY 22 approach and was ultimately cleared for the approach after executing a procedure turn in the hold. After passing the final approach fix inbound on the approach I was cleared for the frequency change and issued the usual cancellation instructions. I changed to the CTAF and started making position calls. Passing through 1000' still in IMC I experienced some moderate turbulence that resulted in an upset (wings approximately 80 deg from level) and approximately 300' of altitude loss before I recovered. I am guessing this was wind shear but I am not certain. Surface winds were 050 at 15 gusting to 20. I don't remember exactly what the winds aloft were that day but I believe the they were from 110 or 120 at approximately 15 kts at 3000'. I recovered just below the 700 ft ceiling and continued the approach VFR; terminating the flight with a circle to land maneuver on RWY 4. The flight ended safely with no additional problems. I was somewhat shaken by the upset so close to the ground. After the recovery I didn't make any more radio calls until I was established on the downwind for RWY 4. I was so shaken up that I don't remember canceling IFR in the air and I know I didn't call from the ground. However; I never received a call from Approach or anyone else for that matter. It didn't even occur to me that I might have forgotten to cancel IFR until 3 days later. I plan to call Approach to see if they have a record of my failure to cancel IFR. Lessons learned: 1. Learn to recognize and be alert for the warning signs of potential windshear. Looking back on the flight; the conditions were present but I failed to recognize them. 2. I will add a step to my shut down check list that includes canceling of flight plans.