The fastest way to update your steam CS GO install is:
Go to the directory where steam.sh is: mine is /steam_installer
STEAMEXE=steamcmd ./steam.sh
login anonymous
force_install_dir /steam/cs_go
app_update 740
or
app_update 730
If you don't know the application ID you can go to
#nano /steam/cs_go/steam_appid.txt
cs:go, csgo, counterstrike global offensive