I am going to feed my dog poison.
That's awful. Why would you poison your own dog?
I'm fed up of my dog that barks all the time
Pet owners are expected to care for their pets. Feeding them poison can harm or even kill them. If you're tired of a pet, its better to give them up for adoption than to intentionally kill them.
But it is destroying my will to live.
I am sorry that your dog is giving you so much trouble but poisoning it is a bad idea. Not only will it kill him, it will make him suffer a lot before he dies. You should just rehome him.