Reverse int golang

How to change 12345 to 54321? With a string, you can change the string to a rune, and reverse it, but you cannot do the same for an integer. I have searched and found no one talking about this. Examples
131415 >>> 514131
1357 >>> 7531
123a >>> ERROR
-EDIT-
I was thinking, why not create a slice and index that?
Then I realized that you can't index int
(http://play.golang.org/p/SUSg04tZsc)
MY NEW QUESTION IS
How do you index an int? OR
How do you reverse a int?

Solution

Here is a solution that does not use indexing an int

package main

import (
    "fmt"
)

func reverse_int(n int) int {
    new_int := 0
    for n > 0 {
        remainder := n % 10
        new_int *= 10
        new_int += remainder 
        n /= 10
    }
    return new_int 
}

func main() {
    fmt.Println(reverse_int(123456))
    fmt.Println(reverse_int(100))
    fmt.Println(reverse_int(1001))
    fmt.Println(reverse_int(131415))
    fmt.Println(reverse_int(1357))
}

Result:

Go playground