Json Parsing in Golang - json

Question

I am trying to parse a json from a third party software. It returns a json like this
{
"top1/dir1": "10",
"top1/dir2": "20",
"top1/dir3": "30",
"top2/diff_val1": "40"
}
JSONLint says this is a valid json. But I could not figure how I can parse this with golang.
The code I used to parse the json file above (to be clear I took the code from another stackoverflow post).
package main
import (
"encoding/json"
"fmt"
"io/ioutil"
"log"
)
type mytype []map[string]string
func main() {
var data mytype
file, err := ioutil.ReadFile("t1.json")
if err != nil {
log.Fatal(err)
}
err = json.Unmarshal(file, &data)
if err != nil {
log.Fatal(err)
}
fmt.Println(data)
}
When I do a go run main.go, I get the below error
$ go run main.go
2016/06/19 22:53:57 json: cannot unmarshal object into Go value of type main.mytype
exit status 1
I did try to parse this format with another library - "github.com/Jeffail/gabs", but was unsuccessful. Since this is a valid json, I am pretty sure this can be parsed, but I am not sure how.

Answer 1

There is a Go package with methods for decoding JSON strings.
https://golang.org/pkg/encoding/json/#Unmarshal
Here is an example of usage:
package main
import (
"encoding/json"
"fmt"
)
func main() {
var jsonBlob = []byte(`[
{"Name": "Platypus", "Order": "Monotremata"},
{"Name": "Quoll", "Order": "Dasyuromorphia"}
]`)
type Animal struct {
Name string
Order string
}
var animals []Animal
err := json.Unmarshal(jsonBlob, &animals)
if err != nil {
fmt.Println("error:", err)
}
fmt.Printf("%+v", animals)
}
EDIT: As pointed out by Malik, the type of the value whose pointer you pass is wrong. In this case, your type should be map[string]interface{} (preferably, because a JSON field might not store a string) or map[string]string instead of []map[string]string. The brackets at the beginning are wrong: such would be an array of JSON objects.

Answer 2

It's just that you have a small typo in your program. You've declared mytype as a slice of maps, rather than just a map.
Just change:
type mytype []map[string]string
To:
type mytype map[string]string
See https://play.golang.org/p/pZQl8jV5TC for an example.

Answer 3

Jonathan's answer provides a good example of decoding JSON, and links the relevant package. You don't provide much detail on what exactly is going wrong with your parsing, but if I had to take a guess I would say you're probably not creating an appropriate struct to contain the JSON once it is unmarshalled. Because Go is statically typed, it expects data to adhere to explicitly defined formats.
If you don't want to go to the trouble of defining structs, you could just use an empty interface object, which is sort of a catch all in Go. Simply declare a variable with the type []interface{}, and then pass it into the JSON unmarshal function. Hope this helps!