JSON解码值被视为float64而不是int

I have a json response from a api as map[message:Login Success. userid:1]

Server:

c.JSON(200, gin.H{"message": "Login Success.", "userid": 1})

Client:

var result map[string]interface{}
json.NewDecoder(resp.Body).Decode(&result)

msg, ok := result["message"].(string)
if !ok {
    msg = "Something went wrong."
}
userID, ok := result["userid"].(int)
if !ok {
    userID = 0
}

But userID, ok := result["userid"].(int) always fails. I've even tried using:

switch v := x.(type) {
case nil:
    fmt.Println("x is nil")          
case int: 
    fmt.Println("x is", v)           
case bool, string:
    fmt.Println("x is bool or string")
default:
    fmt.Println("type unknown")      
}

And it just gave me unknown. Why is the integer not being taken as integer?

It looks like its treating the value as float64.