My bike lock became increasingly hard to unlock over the past few weeks, for the past week or so it became so hard to open that I usually had to put a hammer or find a stone or piece of wood to put on the key handle to twist it. But today after college even with a variety of stones and sticks it refused to turn, and in the end I managed to get the key to rotate slowly. But after some tries when I pulled it out, I realized that it was really the key itself that was twisting and not the lock... Kol
I carried my bike to a nearby bike shop, then they sprayed something like WD 40 into the keyhole and unlocked it with my reserve key... The lock is still problematic but it's better now, and I bought a spray so hopefully I can fix it myself now in the future.