code: func newBootTimeCollector() (Collector, error) {
  	return &bootTimeCollector{
  		boottime: bsdSysctl{
  			name:        "boot_time_seconds",
  			description: "Unix time of last boot, including microseconds.",
  			mib:         "kern.boottime",
  			dataType:    bsdSysctlTypeStructTimeval,
  		},
  	}, nil
  }
docs: // newBootTimeCollector returns a new Collector exposing system boot time on BSD systems.