package opts import ( "fmt" "net" ) // IpOpt type that hold an IP type IpOpt struct { *net.IP } func NewIpOpt(ref *net.IP, defaultVal string) *IpOpt { o := &IpOpt{ IP: ref, } o.Set(defaultVal) return o } func (o *IpOpt) Set(val string) error { ip := net.ParseIP(val) if ip == nil { return fmt.Errorf("%s is not an ip address", val) } *o.IP = ip return nil } func (o *IpOpt) String() string { if *o.IP == nil { return "" } return o.IP.String() }