Parsing nested JSON in go language

How could I parse and extract certain values from below JSON

Here is the sample JSON response

{
"success":true,
"endpoint":"https://api.abcxyz.com",
"info":{
"Guestconnected":134,
"Guestratio":100000.06963,
"symbol1":{
"code":"NY",
"symbol":"*",
"name":"newyear",
"codev":391.78161,
"symbolAppearsAfter":false,
"local":true
},
"symbol2":{
"code":"HNY",
"symbol":"@",
"name":"HappyNewYear",
"codev":1000000.0960,
"symbolAppearsAfter":true,
"local":false
},
"latest":{
"value":1597509,
"autovalue":"00099cf8da58a36c08f2ef98650ff6043ddfb",
"height":474696,
"time":1499527696
}
},
"Allguest":{
"all":4,
"filtered":4,
"total_invitations":15430,
"sent_invitations":15430,
"final_invitations":0
},
"Guestlist":[
{
"GuestCode":"369AR",
"all":2,
"total_invitations":5430,
"sent_invitations":5430,
"final_invitations":0,
"change":0,
"accounts":0
},
{
"GuestCode":"6POIA96TY",
"all":2,
"total_invitations":10000,
"sent_invitations":10000,
"final_invitations":0,
"change":0,
"accounts":0
}
]
}

My Code is :

package main
import (
"encoding/json"
"fmt"
"log"
"net/http"
)
type object struct {
Success bool `json:"success"`
Endpoint string `json:"endpoint"`
Allguest struct {
All int `json:"all"`
Filtered int `json:"filtered"`
TotalInvitations int `json:"total_invitations"`
SentInvitations int `json:"sent_invitations"`
FinalInvitations int `json:"final_invitations"`
} `json:"Allguest"`
Guestlist []struct {
GuestCode string `json:"GuestCode"`
All int `json:"all"`
TotalInvitations int `json:"total_invitations"`
SentInvitations int `json:"sent_invitations"`
FinalInvitations int `json:"final_invitations"`
Change int `json:"change"`
Accounts int `json:"accounts"`
} `json:"Guestlist"`
}
func main() {
uri := "https://siteurl.com/api?lists=1"
res, err := http.Get(uri)
fmt.Println(uri)
if err != nil {
fmt.Println("Error:", err)
log.Fatal(err)
}
defer res.Body.Close()
var s object
err := json.NewDecoder(res.Body).Decode(&s)
if err != nil {
log.Fatal(err)
fmt.Println("Error:", err)
}
fmt.Println(s.Success)
fmt.Println(s.Allguest.TotalInvitations)
for i := 0; i < 6; i++ {
fmt.Println(s.Guestlist[i].TotalInvitations)
)
}

The problem is :

1. If the response is null it is giving index out of range error how can we avoid this ?

2. Applying condition if TotalInvitations value is greater than 100 then save in 100.csv else save in others.csv

If you need only certain entries from JSON you can define a structure with only those fields you are interested in. And if value can be null it is better to declare a pointer in the structure. Please take a look at an example at go playground: https://play.golang.org/p/mEwSXvPg3D

use gjson pkg to get value from json document an simple way

example:

package main
import (
"fmt"
"github.com/tidwall/gjson"
)
func main() {
data := []byte(`{
"success": true,
"endpoint": "https://api.abcxyz.com",
"info": {
"Guestconnected": 134,
"Guestratio": 100000.06963,
"symbol1": {
"code": "NY",
"symbol": "*",
"name": "newyear",
"codev": 391.78161,
"symbolAppearsAfter": false,
"local": true
},
"symbol2": {
"code": "HNY",
"symbol": "@",
"name": "HappyNewYear",
"codev": 1000000.096,
"symbolAppearsAfter": true,
"local": false
},
"latest": {
"value": 1597509,
"autovalue": "00099cf8da58a36c08f2ef98650ff6043ddfb",
"height": 474696,
"time": 1499527696
}
},
"Allguest": {
"all": 4,
"filtered": 4,
"total_invitations": 15430,
"sent_invitations": 15430,
"final_invitations": 0
},
"Guestlist": [
{
"GuestCode": "369AR",
"all": 2,
"total_invitations": 5430,
"sent_invitations": 5430,
"final_invitations": 0,
"change": 0,
"accounts": 0
},
{
"GuestCode": "6POIA96TY",
"all": 2,
"total_invitations": 10000,
"sent_invitations": 10000,
"final_invitations": 0,
"change": 0,
"accounts": 0
}
]
}
`)
r := gjson.GetBytes(data, "Allguest.total_invitations")
fmt.Println(r.Value()) // output 15430
r = gjson.GetBytes(data, "Guestlist.#.total_invitations")
fmt.Println(r.Value()) // output [5430 10000]
}

> If the response is null it is giving index out of range error how can
> we avoid this?

Unless I'm misunderstanding you, the response being null shouldn't matter.  If you receive 2 Guestlist items, you can only loop over those 2, meaning `for i := 0; i < 6; i++` is wrong.  Change it to `for i := 0; i < len(s.Guestlist); i++` or `for i := range s.Guestlist`.

> Applying condition if TotalInvitations value is greater than 100 then
> save in 100.csv else save in others.csv

You will probably want the `os` package's [`Create`](https://golang.org/pkg/os/#Create) function to create a new file for writing or the [`OpenFile`](https://golang.org/pkg/os/#OpenFile) function, the [`O_CREATE`, `O_WRONLY`, and `O_APPEND`](https://golang.org/pkg/os/#O_WRONLY) file-open flags, and you can pass `0755` as the permission mode (or another set of octal permissions if you want to change access of a file).
You can then use `csvWriter := csv.NewWriter(csvFile)` to wrap the resulting `io.Writer` (assuming there is no error opening the file).  From there, you can just write whatever information you require to the file as CSV records.  Don't forget to call `csvWriter.Flush` to flush the output buffer and `csvWriter.Error` to check whether there was an error flushing the output buffer.  Also don't forget to close the file you opened.