JSON Serialization of Emoji in Go

I recently found Golang suffers JSON serialization for emoji like 😀. The main reason was QuoteToASCII() method converted emoji into utf16 representation like U+00000000 which could not be serialized in JSON. The solution is dividing emoji into high and low runes and modifies them into \u0000 forms then concats them again.

package main

import (
    "encoding/json"
    "fmt"
    "strconv"
    "strings"
    "unicode/utf16"
)

func convertToSafeString(s string) string {
    ns := ""
    for _, char := range s {
        h, l := utf16.EncodeRune(char)
        if h != '\uFFFD' && l != '\uFFFD' {
            safe := strings.ReplaceAll(fmt.Sprintf("%U%U", h, l), "U+", "\\u")
            ns += strings.ToLower(safe)
        } else {
            qs := strconv.QuoteToASCII(string(char))
            ns += qs[1 : len(qs)-1] // remove quotes surrounding string
        }
    }
    return ns
}

func main() {

    s := "😀😀안녕 hi😀🎅🎅🤶🤶🎆🎇🎇"
    ns := convertToSafeString(s)

    println(s, ns)

    var msg map[string]interface{}
    m := fmt.Sprintf(`{"message":"Success %s","ok":true}`, ns)
    json.Unmarshal([]byte(m), &msg)
    fmt.Println(msg)
}

Reference

• https://dev.to/matthewdale/sending-in-go-46bf