Get name of the weekday of a date in Postgresql

CREATE OR REPLACE FUNCTION dayOfWeek (date Date) RETURNS Character Varying(15) AS $$
DECLARE
	DAY_OF_WEEK_CONST Character Varying(15) := 'dow';
 
	dayOfWeek Integer := 0;
	dayName Character Varying(15) := 'Test';
BEGIN
 
	dayOfWeek := date_part(DAY_OF_WEEK_CONST, Date);
 
	IF dayOfWeek = 0 THEN
		dayName := 'Sunday';
	ELSEIF dayOfWeek = 1 THEN
		dayName := 'Monday';
	ELSEIF dayOfWeek = 2 THEN
		dayName := 'Tuesday';
	ELSEIF dayOfWeek = 3 THEN
		dayName := 'Wednesday';
	ELSEIF dayOfWeek = 4 THEN
		dayName := 'Thursday';
	ELSEIF dayOfWeek = 5 THEN
		dayName := 'Friday';
	ELSEIF dayOfWeek = 6 THEN
		dayName := 'Saturday';
	END IF;
	RETURN dayName;
END;
$$ LANGUAGE plpgsql;