How do i change the airspeed so i can surf?

I’ve tried changing sv_airaccelerate on Garry’s Mod, and it isn’t there. sv_airaccelerate on CS:S Makes it so you can surf, anyone know how i can surf on Garry’s Mod?

There command used to be there but isn’t anymore. I’ve been looking for a way to change it too.

I dont know how in gmod