-- get user data and lock that row
SELECT some_column FROM users WHERE id = 2 FOR UPDATE INTO my_var;

-- just lock another rows
SELECT some_column FROM users WHERE id IN(4,7) FOR UPDATE;

WITH t AS(
    UPDATE users
    SET some_column = some_column
    WHERE id IN(2,4,7)
    returning some_column
)
SELECT some_column FROM t WHERE id = 2
INTO my_var;