antivirus issue

antivirus is blocking steam from either downloading or updating the game. i get the error 'content file locked'. the antivirus i am using is avast free antivirus and in order to update or download the game i would need to disable one of its core shields temporarily, which is called file shield. researched this issue online but couldnt find a solution. i should also mention that i only have this problem when downloading path of exile, i get no problems when downloading other games.