Cannot Range Over List Type Interface {} In Function Using Go.

* for me is important then i execute for in a function.

How can fix?

```
package main

import (
    "fmt"
)

type MyBoxItem struct {
    Name string
}

type MyBox struct {
    Items []MyBoxItem
}

func (box *MyBox) AddItem(item MyBoxItem) []MyBoxItem {
    box.Items = append(box.Items, item)
    return box.Items
}

func PrintCustomArray(list interface{}) interface{}  {
    //items := reflect.ValueOf(list)
    for _, v := range list {
        fmt.Println(v.Key,v.Value)
    }
    return 0
}
func main() {

    items := []MyBoxItem{}
    item := MyBoxItem{Name: "Test Item 1"}
    box := MyBox{items}
    box.AddItem(item)
    fmt.Println((box.Items))
    PrintCustomArray(box.Items)
}

```

<https://play.golang.org/p/ZcIBLMliq3>

Error : `cannot range over list (type interface {})`

How can fix?