In using Golang, we sometimes need to parse a JSON data without knowing or specifying a
concrete type struct. We can do this by converting (json.Unmarshal) JSON data into an interface{}.
We can then use it like a map. Accessing it like for example m[“username”].(string)
Below is an example application that converts a JSON string into an interface{}. The statements from line 18 to 23 implements the JSON unmarshall without a concrete struct.
1package main
2
3import (
4 "encoding/json"
5 "log"
6)
7
8var sampleJson = `{
9 "username": "johnpili",
10 "password": "L3akyPa5sw0rd!",
11 "name": "John Pili",
12 "website": "https://johnpili.com",
13 "number": 123
14}`
15
16func main() {
17 rawData := []byte(sampleJson)
18 var payload interface{} //The interface where we will save the converted JSON data.
19 err := json.Unmarshal(rawData, &payload) // Convert JSON data into interface{} type
20 if err != nil {
21 log.Fatal(err)
22 }
23 m := payload.(map[string]interface{}) // To use the converted data we will need to convert it into a map[string]interface{}
24
25 log.Printf("Username: %s", m["username"].(string))
26 log.Printf("Password: %s", m["password"].(string))
27 log.Printf("Name: %s", m["name"].(string))
28 log.Printf("Website: %s", m["website"].(string))
29 log.Printf("Number: %d", int(m["number"].(float64)))
30}
Console Output
