package main

import (
	"encoding/json"
	"github.com/spf13/cast"
	"log"
)

type msg struct {
	Field1 string                 `json:"field1"`
	Extra  map[string]interface{} `json:"extra"`
}

func main() {
	teststring := `{"field1":"dafdaf","extra":{"uids":[1,2,3,4,5,6,7,8]}}`

	var task msg
	if err := json.Unmarshal([]byte(teststring), &task); err != nil {
		log.Fatal("unmarshall")
	}

	log.Printf("%#v", task)

	uidsUntyped, ok := task.Extra["uids"]

	log.Printf("%#v", uidsUntyped)

	if !ok {
		log.Fatal("unmap")
	}
	uids, ok := uidsUntyped.([]uint64)

	log.Printf("%#v", uids)
	uid, _ := cast.ToUint64E(uidI)
	if !ok {
		log.Print(uids)
		log.Fatal("cast")
	}
	log.Print(uids)

}