Upgrade v2ray core to v5

[smf8]

Hi, I don't think this project is maintained anymore. Also, I'm not sure if this still is the best tool to test vmess servers in go. But since I wanted to run this project and the v4 version won't run with go 1.19 or 1.20. I think this workaround might come in handy. Please let me know if anything else should be done. Thank you