如何在使用json.marshal时将嵌套结构名称小写？

package main

import (
    "encoding/json"
    "fmt"
    "reflect"
    "strings"
)

type User struct {
    Name    string `json:"name"`
    Age     int    `json:"age"`
    Address Address
}

type Address struct {
    Street  string `json:"street"`
    City    string `json:"city"`
    Country string `json:"country"`
}

func main() {
    user := User{
        Name: "John",
        Age:  30,
        Address: Address{
            Street:  "123 Main St",
            City:    "New York",
            Country: "USA",
        },
    }

    data, err := json.MarshalIndent(user, "", "  ")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }

    // Convert struct field names to lowercase
    data = convertStructFieldNamesToLowercase(data)

    fmt.Println(string(data))
}

// Function to convert struct field names to lowercase
func convertStructFieldNamesToLowercase(data []byte) []byte {
    // Unmarshal the JSON into a map
    var m map[string]interface{}
    err := json.Unmarshal(data, &m)
    if err != nil {
        fmt.Println("Error:", err)
        return data
    }

    // Recursively convert field names to lowercase
    convertFieldNamesToLowercase(m)

    // Marshal the modified map back to JSON
    result, err := json.MarshalIndent(m, "", "  ")
    if err != nil {
        fmt.Println("Error:", err)
        return data
    }

    return result
}

// Recursive function to convert field names to lowercase
func convertFieldNamesToLowercase(m map[string]interface{}) {
    for k, v := range m {
        switch v := v.(type) {
        case map[string]interface{}:
            convertFieldNamesToLowercase(v)
        case []interface{}:
            convertSliceFieldNamesToLowercase(v)
        }

        // Convert field name to lowercase
        delete(m, k)
        m[strings.ToLower(k)] = v
    }
}

// Function to convert field names in a slice to lowercase
func convertSliceFieldNamesToLowercase(slice []interface{}) {
    for _, v := range slice {
        if m, ok := v.(map[string]interface{}); ok {
            convertFieldNamesToLowercase(m)
        }
    }
}