Does the Gospel of Mark End at 16:20, or 16:8?

Where does the gospel of Mark end?
“I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book”—Revelation 22:18 NKJV
Promoters and believers in faith healing often use Mark 16:17-18 as Biblical support for their healing practices:
“They will lay their hands on the sick and they will recover” (Mark 16:18 NKJV).
SNAKE HANDLING AND DRINKING POISON
These last few verses of Mark are very important to snake handling “Christians” because they say: “They will take up serpents” (Mark 16:18 NKJV). The Weymouth translation reads, “They shall take up venomous snakes”.