Eating cinnamon in some food or mixing some cinnamon with a beverage such as a cup of coffee is not harmful and will not kill you no matter how much of it you drink or eat.
However cinnamon if taken by the spoonful could kill you as it can dry out your throat and cause a blockage in your throat causing you to start coughing and making it hard to breathe.
There have been some people who were doing a cinnamon challenge and eating a bunch of cinnamon and some people have choked and died as a result of it.
So do not eat the cinnamon directly off a spoon and put it in baked goods or in some coffee etc if you want to consume some cinnamon.