如果结构体中带有time.Timer类型的字段，无论是否可导出都无法Marshal


```go
type Test struct {
	t time.Timer
}

func main() {
	t := new(Test)
	data, err := jsoniter.Marshal(t)
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error:", err)
		return
	}

	fmt.Println(string(data))
}
```

## output
> Error: [optional]: [main.Test]: [time.Timer]: unsupported type: <-chan time.Time