Go flag and reflection example.

flag_reflection.go

func FlagReflection(args []string) error {
  opts := map[string]interface{}{}
	flags := flag.NewFlagSet("xxxx", flag.ContinueOnError)
	opts["vcpu"] = flags.Int("vcpu", int(mdst.MinVcpu), "")
	opts["memory_gb"] = flags.Int("memory_gb", int(mdst.MinMemoryGb), "")
	if err := flags.Parse(args); err != nil {
		return err
	}
	flags.Visit(func(f *flag.Flag) {
		v := reflect.ValueOf(mdst)
		fv := reflect.ValueOf(opts[f.Name])
		for i := 0; i < v.Elem().NumField(); i++ {
			jsonTag, ok := v.Elem().Type().Field(i).Tag.Lookup("json")
			if !ok {
				continue
			}
			tagV := strings.Split(jsonTag, ",")
			if tagV[0] == f.Name {
				field := v.Elem().Field(i)
				fmt.Println(reflect.ValueOf(f.Value).Elem().Type())
				fmt.Println(v.Elem().Type().Field(i))
				fmt.Println(v.Elem().Type().Field(i).Name)
				fmt.Println(field.IsValid())
				fmt.Println(field.CanSet())
				fmt.Println(field.CanAddr())
				fmt.Println(field.CanInterface())
				fmt.Println(field.Kind())
				fmt.Println(field.Interface())
				fmt.Println(fv.Elem())
				field.Set(fv.Elem().Convert(field.Type()))
			}
		}
	})
  return nil
}