"Poor goalkeeping" refers to a goalkeeper's performance that is not very good or satisfactory. It means they made mistakes or did not play well in their role of protecting the team's goal from the opposing team's shots. Full definition
Poor defending by lining up with Coq playing on their entire attack but MOSTLY poor goalkeeping. (justarsenal.com)
It was some pretty poor defending from David Luiz and some equally poor goalkeeping from Kevin Trapp, but some excellent play by de Bruyne. (caughtoffside.com)