This. It’s realistic in the sense of it’s the punishment described in US Code Title 18 for treason.
Whoever, owing allegiance to the United States, levies war against them or adheres to their enemies, giving them aid and comfort within the United States or elsewhere, is guilty of treason and shall suffer death, or shall be imprisoned not less than five years and fined under this title but not less than $10,000; and shall be incapable of holding any office under the United States.
Now in the sense of is it a smart punishment or likely? No, it’s not realistic. It would be absolutely idiotic to make him a martyr like that, and as best as I can tell, nobody’s actually been executed for treason since 1862.