Create the user 'reading_user' and giving him permissions
CREATE USER reading_user WITH PASSWORD 'reading_pass';
GRANT CONNECT ON DATABASE my_database TO reading_user;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO reading_user;
GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO reading_user;
GRANT USAGE ON SCHEMA public TO reading_user;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO reading_user;