How to play CSGO after the release of CS2?Guide
1) Download "csgo_legacy" from CS2 beta branches.
2*) Replace the first line in "C:\Program Files (x86)\Steam\steamapps\common\Counter-Strike Global Offensive\csgo\steam.inf" with "ClientVersion=2000258".
3**) Add "C:\Program Files (x86)\Steam\steamapps\common\Counter-Strike Global Offensive\csgo.exe" as a Non-Steam game.
4**) Add "-steam" to the launch options.
* - Fixes connection to CSGO Network
** - Optional for convenience.