Exporting JSON into single file from loop function - json

Question

I wrote some code which hits one public API and saves the JSON output in a file. But the data is storing line by line into the file instead of a single JSON format.
For eg.
Current Output:
{"ip":"1.1.1.1", "Country":"US"}
{"ip":"8.8.8.8", "Country":"IN"}
Desired Output:
[
{"ip":"1.1.1.1", "Country":"US"},
{"ip":"8.8.8.8", "Country":"IN"}
]
I know this should be pretty simple and i am missing out something.
My Current Code is:
To read IP from file and hit the API one by one on each IP.
func readIPfromFile(filename string, outFile string, timeout int) {
data := jsonIn{}
//open input file
jsonFile, err := os.Open(filename) //open input file
...
...
jsonData := bufio.NewScanner(jsonFile)
for jsonData.Scan() {
// marshal json data & check for logs
if err := json.Unmarshal(jsonData.Bytes(), &data); err != nil {
log.Fatal(err)
}
//save to file
url := fmt.Sprintf("http://ipinfo.io/%s", data.Host)
GetGeoIP(url, outFile, timeout)
}
}
To make HTTP Request with custom request header and call write to file function.
func GetGeoIP(url string, outFile string, timeout int) {
geoClient := http.Client{
Timeout: time.Second * time.Duration(timeout), // Timeout after 5 seconds
}
req, err := http.NewRequest(http.MethodGet, url, nil)
if err != nil {
log.Fatal(err)
}
req.Header.Set("accept", "application/json")
res, getErr := geoClient.Do(req)
if getErr != nil {
log.Fatal(getErr)
}
if res.Body != nil {
defer res.Body.Close()
}
body, readErr := ioutil.ReadAll(res.Body)
if readErr != nil {
log.Fatal(readErr)
}
jsonout := jsonOut{}
jsonErr := json.Unmarshal(body, &jsonout)
if jsonErr != nil {
log.Fatal(jsonErr)
}
file, _ := json.Marshal(jsonout)
write2file(outFile, file)
}
To Write data to file:
func write2file(outFile string, file []byte) {
f, err := os.OpenFile(outFile, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
if err != nil {
log.Fatal(err)
}
defer f.Close()
if _, err = f.WriteString(string(file)); err != nil {
log.Fatal(err)
}
if _, err = f.WriteString("\n"); err != nil {
log.Fatal(err)
}
I know, i can edit f.WriteString("\n"); to f.WriteString(","); to add comma but still adding [] in the file is challenging for me.

Answer 1

First, please do not invent a new way of json marshaling, just use golang built-in encoding/json or other library on github.
Second, if you want to create a json string that represents an array of object, you need to create the array of objects in golang and marshal it into string (or more precisely, into array of bytes)
I create a simple as below, but please DIY if possible.
https://go.dev/play/p/RR_ok-fUTb_4