I’m trying to convert JSON to a generic struct in Go, where the struct can have fields with varied types. To handle different types of data, I’m using the interface{} type in the struct fields. However, I don’t know the exact structure of the JSON object that will be unmarshalled, so I need a flexible solution. When I unmarshal the JSON, I end up with a map[string]interface{}, but I want to get an object (struct).

For example, given this JSON:

{
  "animal": "Elephant",
  "age": 15,
  "location": {
    "country": "Kenya",
    "continent": "Africa"
  },
  "diet": ["grass", "fruit", "vegetables"]
}

Here is the Go code I am using:

package main

import (
    "encoding/json"
    "fmt"
)

type GenericStruct struct {
    Animal   interface{} `json:"animal"`
    Age      interface{} `json:"age"`
    Location interface{} `json:"location"`
    Diet     interface{} `json:"diet"`
}

func main() {
    jsonData := `{
        "animal": "Elephant",
        "age": 15,
        "location": {
            "country": "Kenya",
            "continent": "Africa"
        },
        "diet": ["grass", "fruit", "vegetables"]
    }`
    
    var result GenericStruct
    
    err := json.Unmarshal([]byte(jsonData), &result)
    if err != nil {
        fmt.Println("Error:", err)
    }
    
    fmt.Printf("Result: %+vn", result)
}

Instead of getting a map[string]interface{}, I want to directly unmarshal into a struct with interface{} fields, so that I can handle the varied types more easily.

Current output:

map[age:15 animal:Elephant diet:[grass fruit vegetables] location:map[continent:Africa country:Kenya]]

Desired output (as an object):

{Animal:Elephant Age:15 Location:{Country:Kenya Continent:Africa} Diet:[grass fruit vegetables]}

I tried using mapstructure.Decode(data, &result) but it didn’t work either.

How can I achieve this in Go? Am I missing some Go concept to make this work correctly?