SubSelect as a column

I am trying to use a subselect as a column name, but it appears as if this
is not supported in Postgresql. Here is the query:

SELECT u.idnum, u.username,
(SELECT COUNT(t.techid)
FROM ticket t
WHERE t.techid = u.idnum)
FROM users u;

the desired output would be:

idnum|username|?column?
-----+--------+--------
6|lomboy | 3
2|stuart | 6
4|trevor | 0
9|victor | 0

I can do this with the INNER JOIN:

SELECT u.idnum, MAX(u.username), COUNT(t.techid)
FROM users u, ticket t
WHERE t.techid = u.idnum
GROUP BY u.idnum;

But this will only return the those Whose count is not 0:

idnum|username|?column?
-----+--------+--------
6|lomboy | 3
2|stuart | 6

I have tried in vain to figure out how to do this correctly, but I am at a
loss. Any advice on how to get this to work.

Thank you very much in advance,

-Lars