decode_json.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"log"
)

var s = `
[{
    "video": [
        1,
        2,
        3
    ],
    "video_type": "template_a"
},
{
    "video": {
        "a": {
            "aa": []
        }
    },
    "video_type": "template_b"
}]
`

type sliceVideo []int

type objectVideo struct {
	A struct {
		Aa []any `json:"aa"`
	} `json:"a"`
}

type template struct {
	VideoType string          `json:"video_type"`
	VideoRaw  json.RawMessage `json:"video"`
	Video     interface{}
}

func main() {
	buf := bytes.NewBuffer([]byte(s))
	decoder := json.NewDecoder(buf)
	var templates []*template
	err := decoder.Decode(&templates)
	if err != nil {
		log.Fatalln(err)
	}
	for _, t := range templates {
		switch t.VideoType {
		case "template_a":
			t.Video = &sliceVideo{}
		case "template_b":
			t.Video = &objectVideo{}
		}
		err := json.Unmarshal(t.VideoRaw, &t.Video)
		if err != nil {
			log.Fatalln(err)
		}
	}
	for _, v := range templates {
		fmt.Printf("%s: %v\n", v.VideoType, v.Video)
	}
}