Go module to get the number of CPUs (library)

 The package numcpus provides information about the number of CPU in a system.
 .
 It gets the number of CPUs (online, offline, present, possible,
 configured or kernel maximum) on a Linux, Darwin, FreeBSD, NetBSD,
 OpenBSD, DragonflyBSD or Solaris/Illumos system.
 .
 On Linux, the information is retrieved by reading the corresponding CPU
 topology files in /sys/devices/system/cpu.