package main

import  ( 
  "fmt"
  "encoding/hex"
  "encoding/base64"
  "crypto/hmac"
  "crypto/sha256"
)

func main() {
  x := makeHmac("abcdef","1234567890")
  fmt.Printf("%s\n", x)
}

func makeHmac(data string, key string) string {
  byteKey, _ := hex.DecodeString(key)  
  byteData := []byte(data)
  sig := hmac.New(sha256.New, byteKey)
  sig.Write([]byte(byteData))
  return base64.StdEncoding.EncodeToString(sig.Sum(nil))
}