I created a group on a Linux machine. Now I am trying to call
func Chown(name string, uid, gid int) error
Update: As of August 16, 2016, Go 1.7 is released with support for LookupGroup. Upgrading to Go 1.7 is recommended if you want to access information about POSIX groups.
There is a LookupGroup function in the Go 1.7 betas, but it was added only this February and isn't in any released version of Go, so you're kind of out of luck.
As far as I can see your options are:
getgrnamfor the information you need (tricky)
/etc/group(relatively easy... as long as you can guarantee that the info you need actually comes from that file and not LDAP or something).