Example of update trigger to set updated_at to current timestamp

create_table_foobar.sql

CREATE TABLE IF NOT EXISTS foobar (
    id            UUID          PRIMARY KEY DEFAULT gen_random_uuid(),
    created_at    TIMESTAMPTZ   NOT NULL DEFAULT timezone('utc', now()),
    updated_at    TIMESTAMPTZ
);

CREATE OR REPLACE FUNCTION foobar_table_but()
    RETURNS TRIGGER
    LANGUAGE plpgsql
    AS '
    BEGIN
        NEW.updated_at := timezone(''utc'', now());
        RETURN NEW;
    END;
';

CREATE TRIGGER foobar_table_but
    BEFORE UPDATE ON foobar
    FOR EACH ROW EXECUTE PROCEDURE foobar_table_but();