为什么golang json数字不能转换int或字符串int，如“ 10”？

I want convert interface value to number, but when interface is number or number string, it will not work, I do not know why we can't convert by this way?

package main

import (
    "encoding/json"
    "fmt"
    "reflect"
)

func main() {
    number := 10
    strNumber := "10"
    test(number)
    test(strNumber)
}

func test(i interface{}) {
    strNum, ok := i.(json.Number)
    fmt.Println(strNum, ok, reflect.TypeOf(i))
}

It will produce result like this:

   false int
   false string

Here's your example in Go:

package main

import (
    "encoding/json"
    "fmt"
    "strconv"
)

func main() {
    number := 10
    strNumber := "10"
    test(number)
    test(strNumber)
}

func test(i interface{}) {
    var strNum string
    switch x := i.(type) {
    case int:
        strNum = strconv.Itoa(x)
    case string:
        if _, err := strconv.ParseInt(x, 10, 64); err == nil {
            strNum = x
        }
    }
    jsonNum := json.Number(strNum)
    fmt.Printf("%[1]v %[1]T
", jsonNum)
}

Playground: https://play.golang.org/p/iDSxrORX9yc

Output:

10 json.Number
10 json.Number