Go中Linux上的八进制文件烫发位

I am trying to get file permission bits in Octal representation. The below code prints it as string. Is there an API to print in Octal or int?

import "os"
import "fmt"

func main() {
    m, _ := os.Stat("test.go")
    perm := m.Mode().Perm()
    fmt.Println(perm)
}   

$:~/gocode/ws/gocode$ go run perm.go 
-rw-rw-r--
@:~/gocode/ws/gocode$ 

For example,

package main

import (
    "fmt"
    "os"
    "strconv"
)

func main() {
    fi, err := os.Stat("test.go")
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    perm := fi.Mode().Perm()
    fmt.Println(perm)
    fmt.Printf("%o
", perm)
    fmt.Printf("%#o
", perm)
    fmt.Println(strconv.FormatUint(uint64(perm), 8))
    fmt.Println("0" + strconv.FormatUint(uint64(perm), 8))
}

Output:

-rw-rw-r--
664
0664
664
0664