Listing files of container returns wrong response about codetainer HOT 2 CLOSED

package main

import (
        "encoding/json"
        "fmt"
)

type Foo struct {
        Apple string `json:"field1"`
        Banana string `json:"field2"`
}

func main() {
        var f Foo
        str := `{ "Apple": "app", "field2": "ban" }`
        json.Unmarshal([]byte(str), &f)
        fmt.Println(f)
        s, err := json.Marshal(f)
        if err != nil {
                fmt.Println("err")
        }
        fmt.Println(string(s))
}

{ ban}
{"field1":"","field2":"ban"}