Hello,

This is not really reporting defects but more like a feature request.

In syscall package, or go.sys package, Sysctl is defined as: 

func Sysctl(name string) (value string, err error)

It provides a way to read values through sysctl, but makes it impossible to write/update
values. Internally, it uses "sysctl" defined in each particular OS / ARCH. For
example, (from zsyscall_freebsd_amd64.go):

func sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err
error)

It would be nice if it can be exported in some way because this is essentially the same
interface as defined in BSD systems. e.g. https://www.freebsd.org/cgi/man.cgi?sysctl(3)

int sysctl(const int *name, u_int namelen, void *oldp, size_t *oldlenp, const void
*newp, size_t newlen);
int sysctlbyname(const char *name, void *oldp, size_t *oldlenp, const void *newp, size_t
newlen);

Can we provide a similar set of functions in go.sys that provides full sysctl support
(both read / write)? If go.sys is not frozen yet, maybe it's a good idea to use the
function names used in most BSD systems, in which case current Sysctl will need to be
renamed to, e.g., SysctlRead.