how to get previous month from current date in postgresql code example

Example 1: postgresql get last day of month

create function end_of_month(date)
returns date as
$$
select (date_trunc('month', $1) + interval '1 month' - interval '1 day')::date;
$$ language 'sql'
immutable strict;

Example 2: postgresql get last day of month

SELECT (date_trunc('month', '2017-01-05'::date) + interval '1 month' - interval '1 day')::date
AS end_of_month;