go change json key struct

package main

import (
    "encoding/json"
    "fmt"
)

type OriginalStruct struct {
    OldKey string `json:"old_key"`
}

type ModifiedStruct struct {
    NewKey string `json:"new_key"`
}

func main() {
    // Create an instance of the original struct
    originalInstance := OriginalStruct{OldKey: "value"}

    // Convert the original struct to JSON
    originalJSON, err := json.Marshal(originalInstance)
    if err != nil {
        fmt.Println("Error marshalling original struct:", err)
        return
    }
    fmt.Println("Original JSON:", string(originalJSON))

    // Unmarshal the JSON into the modified struct
    var modifiedInstance ModifiedStruct
    err = json.Unmarshal(originalJSON, &modifiedInstance)
    if err != nil {
        fmt.Println("Error unmarshalling into modified struct:", err)
        return
    }

    // Print the modified struct
    fmt.Println("Modified Struct:", modifiedInstance)
}