func PossibleCPUs() (int, error) {
	sysCPU.once.Do(func() {
		sysCPU.num, sysCPU.err = parseCPUsFromFile("/sys/devices/system/cpu/possible")
	})
	return sysCPU.num, sysCPU.err
}
PossibleCPUs returns the max number of CPUs a system may possibly have
Logical CPU numbers must be of the form 0-n
package internal
import (
	"fmt"
	"io/ioutil"
	"strings"
	"sync"
)
var sysCPU struct {
	once sync.Once
	err  error
	num  int
}