sudo(8) -u postgres psql(1)
execute a command as another user
-u user     The -u (user) option causes sudo to run the specified command as a user other than root.  To
            specify a uid instead of a user name, use #uid.  When running commands as a uid, many shells
            require that the '#' be escaped with a backslash ('\').  Security policies may restrict uids
            to those listed in the password database.  The sudoers policy allows uids that are not in the
            password database as long as the targetpw option is not set.  Other security policies may not
            support this.
PostgreSQL interactive terminal
source manpages: sudopsql