Why Json Unmarshall changing array type in Golang?

Question

I'm trying to seed my Postgres database as functionally. In my case, SeedSchema() function can take any type struct. So I define a interface and create functions to my structs which will seed. I tried with generics and without.

When I unmarshall any json array from file as byte array, json.Unmarshall method change my tempMember member of struct. Exp, models.Term to map[string]interface{}. I've used unmarshall before this function and I've not seen like this situation.

Here is my SeedSchema() function:

func (db *Database) SeedSchema(models ...globals.Seeder[any]) error {
var (
    subjects []globals.Seeder[any]
    fileByte []byte
    err      error
    // tempMember any
)
if len(models) == 0 {
    subjects = seederModelList
} else {
    subjects = models
}
for _, model := range subjects {
    fileName, tempMember := model.Seed()
    fmt.Printf("%+v\n", reflect.TypeOf(tempMember)) //1
    if fileByte, err = os.ReadFile("db/seeds/" + fileName); err != nil {
        fmt.Println(err)
        return err
    }
    if err = json.Unmarshal(fileByte, &tempMember); err != nil {
        fmt.Println(err)
        return err
    }
    fmt.Printf("%+v\n", reflect.TypeOf(tempMember)) //2

}
return nil 
}

First print returns []models.AirportCodes and the second []interface {}.

Here is my interface and model:

func (AirportCodes) Seed() (string, any) {
    return "airport_codes.json", []AirportCodes{}
}

type Seeder[T any] interface {
    Seed() (string, T)
    // Seed(*gorm.DB) error
    TableName() string
}

seederModelList = []globals.Seeder[any]{
        m.AirportCodes{},
        m.Term{},
    }

Answer 1

After a few weeks, I have looking for solve this problem and look unmarshaler interfaces and examples. Then Like what icza said, I started to look over the my code that convention between types and I solved like this. If you guys have better answer than mine, please add answer.

Data:

[
    {
        "id":1,
        "name":"Term 1",
        "content": [
            "a1",
            "a2",
            "a3"
        ]
    }
]

Result:

[{ID:1 Name:Term 1 Content:[a1 a2 a3]}]

UnmarshalJSON Function:

func (term *Term) UnmarshalJSON(data []byte) error {
    tempMap := map[string]interface{}{}
    if err := json.Unmarshal(data, &tempMap); err != nil {
        return err
    }
    *term = Term{
        Name: tempMap["name"].(string),
    }
    if tempMap["content"] != nil {
        for _, v := range tempMap["content"].([]interface{}) {
            (*term).Content = append((term).Content, v.(string))
        }
    }
    return nil
}

Thank you for comments.