resolving user and group ids to names, and listing supplementary group IDs.
One is written in pure Go and parses /etc/passwd and /etc/group. The other
is cgo-based and relies on the standard C library (libc) routines such as
getpwuid_r, getgrnam_r, and getgrouplist.

When cgo is available, and the required routines are implemented in libc
for a particular platform, cgo-based (libc-backed) code is used.
This can be overridden by using osusergo build tag, which enforces