How to use golang to convert a multi-line json to one-line json?

How can I convert a multi-line json to a one-line json using Go?

From:

{
          "release_date": "2004-11-09",
          "status": "retired",
          "engine": "Gecko",
          "engine_version": "1.7"
        }

To:

{"release_date":"2004-11-09","status":"retired","engine":"Gecko","engine_version":"1.7"}

json.Compact() does exactly this:

> func Compact(dst *bytes.Buffer, src []byte) error
> Compact appends to dst the JSON-encoded src with insignificant space characters elided.

json.Compact() is superior to unmarshaling and marshaling again, as it works with any valid JSON, and is much-much faster (it doesn't create and throw away Go values). It's also superior to using any regexp, again, it's much-much faster and regexp does not understand JSON syntax fully, so it might result in data loss.

For example:

func main() {
	dst := &bytes.Buffer{}
	if err := json.Compact(dst, []byte(src)); err != nil {
		panic(err)
	}
	fmt.Println(dst.String())
}

const src = `{
          "release_date": "2004-11-09",
          "status": "retired",
          "engine": "Gecko",
          "engine_version": "1.7"
        }`

This will output (try it on the Go Playground):

{"release_date":"2004-11-09","status":"retired","engine":"Gecko","engine_version":"1.7"}

Unmarshal the multi-line JSON into a struct (or alternatively a map[string]any{}) and then marshal it to a string without any indent options. So, something like this:

	v := struct {
		ReleaseDate string `json:"release_date"`
		Status      string `json:"status"`
		Engine      string `json:"engine"`
		Version     string `json:"engine_version"`
	}{}

	if err := json.Unmarshal([]byte(s), &v); err != nil {
		fmt.Printf("ERROR: %v\n", err)
	} else if bytes, err := json.Marshal(v); err != nil {
		fmt.Printf("ERROR: %v\n", err)
	} else {
		fmt.Printf("%v\n", string(bytes))
	}

(Go Playground)

If you dont know which kind of json you will get
just use like this

package main

import (
	"encoding/json"
	"fmt"
)

const js = `
{
    "release_date": "2004-11-09",
    "status": "retired",
    "engine": "Gecko",
    "1": "1.7"
}
`

func main() {
	helper := make(map[string]interface{})

	err := json.Unmarshal([]byte(js), &helper)
	if err != nil {
		fmt.Printf("json.Unmarshal([]byte(s), &helper) failed. Error:  %v\n", err)
        return
	} 
	
	bytes, err := json.Marshal(helper)
	if err != nil {
		fmt.Printf("json.Marshal(helper) failed. Error:  %v\n", err)
	    return
	}
	
	fmt.Println(string(bytes))
		
}

Try here

And don't use replacing spaces because you can damage json values