go base32 DecodeString解码错误原因

package main

import (
    "encoding/base32"
    "fmt"
    "os"
    "strings"
)

func main() {
    input := os.Args[1]
    inputnospace := strings.Replace(input, " ", "", -1)
    inputnospaceupper := strings.ToUpper(inputnospace)
    key, err := base32.StdEncoding.DecodeString(inputnospaceupper)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(key)
}

错误提示包含指定索引位置,在网上找到了如下答案,只支持A-Z,2-7,=

Your problem is that that input data isn't Base32 encoded. Base32 encoding only uses the characters A-Z (capital only), 2-7, and =