To me that looks like you have synchronous replication and the replica is behind thus your command is waiting for the alter command to be written to the replica’s WAL file. Doing a Ctrl-C terminates the waiting on synchronous replication but the command was already completed on the primary node just not replicated yet.
Can you confirm or deny the use of synchronous replication?
I am doing CIS Benchmart on Postgreql 12. After alter parameters and when I tried to create a new role. It's lagging and didn't prompt out the result, until I hit the ctl C key. Even alter role. All I needed to hit ctl C key if not, it hung there for ever. Is there a way to fix it?
postgres=# create role appuser;
^CCancel request sent
CREATE ROLE
postgres=# ALTER ROLE appuser NOSUPERUSER;
^CCancel request sent
ALTER ROLE
postgres=# ALTER ROLE appuser NOREPLICATION;
^CCancel request sent
ALTER ROLE
postgres=# ALTER ROLE appuser NOCREATEROLE;
^CCancel request sent
ALTER ROLE
postgres=# ALTER ROLE appuser NOHERIT;
^CCancel request sent
ALTER ROLE