func FDLimit() (uint64, error) {
	var rlimit syscall.Rlimit
	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rlimit); err != nil {
		return 0, err
	}
	return rlimit.Cur, nil
}
FDLimit get the open file limit on linux
package nsqdserver
import (
	"syscall"
)