func md5V(str string) string  {
    h := md5.New()
    h.Write([]byte(str))
    return hex.EncodeToString(h.Sum(nil))
}

func md5V2(str string) string {
    data := []byte(str)
    has := md5.Sum(data)
    md5str := fmt.Sprintf("%x", has)
    return md5str
}

func md5V3(str string) string {
    w := md5.New()
    io.WriteString(w, str)
    md5str := fmt.Sprintf("%x", w.Sum(nil))
    return md5str
}

package main

import (
    "crypto/md5"
    "encoding/hex"
    "fmt"
    "io"
)
func main() {
    str := "MD5testing"
    md5Str := md5V(str)
    fmt.Println(md5Str)
    fmt.Println(md5V2(str))
    fmt.Println(md5V3(str))
}
// 输出结果：
f7bb96d1dcd6cfe0e5ce1f03e35f84bf
f7bb96d1dcd6cfe0e5ce1f03e35f84bf
f7bb96d1dcd6cfe0e5ce1f03e35f84bf