Adding a new value to shared_preload_libraries

I want to ask that I have parameter shared_preload_libraries I want to add another value to his parameter how can I add to it. I am using this but it isn’t working.
stolonctl --cluster-name=mycluster $CLUSTER_NAME update -p ‘{“pgParameters”: { “shared_preload_libraries” : “pg_stat_statements,pgaudit”} }’