[postgres@centos7 ~]$ psql -U postgres
psql (12.17)
Type "help" for help.

postgres=# select ssl_is_used();
 ssl_is_used 
-------------
 f
(1 row)
postgres=# exit
[postgres@centos7 ~]$
[postgres@centos7 ~]$ psql -h localhost
psql (12.17)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
Type "help" for help.

postgres=# select ssl_is_used();
 ssl_is_used 
-------------
 t
(1 row)

postgres=# exit
[postgres@centos7 ~]$
[postgres@centos7 ~]$ psql 'host=localhost user=postgres dbname=postgres password=postgres sslmode=require'
psql (12.17)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
Type "help" for help.

postgres=# select ssl_is_used();
 ssl_is_used 
-------------
 t
(1 row)

postgres=# exit
[postgres@centos7 ~]$