How to access fields of a JSON in GO - json

Question

Hi everyone I'm trying to see what the proper way of accessing fields of a json object from a http.get request in go.
I first do an http.get call get the JSON and then print it (which works) but is there a way to access just a field?
for example:
response, err:= http.Get("URL")
//Error checking is done between
contents, err:=ioutil.Readall(response.Body)
//Now at this point I have a json that looks like
{"id": "someID",
"name": "someName",
"test": [{"Name":"Test1",
"Result": "Success"},
{"Name":"Test2",
"Result": "Success"},
{...},
]}
Is there a way to only print the "test" of the Json? What is the proper way of accessing that field?

Answer 1

Use encoding/json package to Unmarshal data into struct, like following.
type Result struct {
ID string `json:"id"`
Name string `json:"name"`
Test []interface{} `json:"test"`
}
var result Result
json.Unmarshal(contents, &result)
fmt.Println(result.Test)
You can also parse Test to specific struct.

Answer 2

Same as the previous answer, use encoding/json package to Unmarshal data. But if you don't want to specify the structure, you could use map[string]interface/bson.M{} to receive the data, and get the field, then cast into types your want.
m := make(map[string]interface{})
err := json.Unmarshal(data, &m)
if err != nil {
log.Fatal(err)
}
fmt.Println(m["id"])

Answer 3

You may want to try gabs container, if you are not sure how depth JSON hierarchy can be. Have a look at below resources
https://github.com/Jeffail/gabs
https://godoc.org/github.com/Jeffail/gabs

Answer 4

If you just want to access one field then you can use the jsonq module https://godoc.org/github.com/jmoiron/jsonq
For your example you could get the test object with code similar to
jq.Object("test")
Where jq is a jsonq query object constructed from your JSON above (see the godoc page for instructions on how to create a query object from a JSON stream or string).
You can also use this library for retrieving specific String, Integer, Float and Bool values at an arbitrary depth inside a JSON object.

Answer 5

Since you are starting with a URL, Decode is a better option than Unmarshal:
package main
import (
"encoding/json"
"net/http"
)
func main() {
r, e := http.Get("https://github.com/manifest.json")
if e != nil {
panic(e)
}
defer r.Body.Close()
var s struct { Name string }
json.NewDecoder(r.Body).Decode(&s)
println(s.Name == "GitHub")
}
https://golang.org/pkg/encoding/json#Decoder.Decode

Answer 6

You may check this https://github.com/valyala/fastjson
s := []byte(`{"foo": [123, "bar"]}`)
fmt.Printf("foo.0=%d\n", fastjson.GetInt(s, "foo", "0"))
// Output:
// foo.0=123