Install of a Electro magnet lock and gate closer

I have an existing metal gate. I would like to have a electromagnet and gate closer fitted to it. Some welding and modification will be required. I would like to know if anyone can advise in which category this type of job should be posted and any general advice. The gate requires access during certain hours for couriers, postman, essential access. During these hours the entry should not be hindered. But the gate should close itself as presently it's left open. During certain hours the gate will need to be locked and access to only person with key/fob/code etc . Any advice on any up to date methods to implement this would be appreciated. Thanks