a go pure disk state interface
// example
func main() {
state := diskstate.DiskUsage("/")
fmt.Printf("All=%dM, Free=%dM, Available=%dM, Used=%dM, Usage=%d%%",
state.All/diskstate.MB, state.Free/diskstate.MB, state.Available/diskstate.MB, state.Used/diskstate.MB, 100*state.Used/state.All)
}