imaginary-sign.go

package main

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

func main() {
	signKey := "averylongandsecurekeywithmin32chars"
	urlPath := "/resize"
	url := "https%3A%2F%2Fwww.google.com%2Flogos%2Fdoodles%2F2015%2Fgoogles-new-logo-5078286822539264.3-hp2x.gif"
	urlQuery := "nocrop=true&type=jpeg&url=" + url + "&width=200"

	h := hmac.New(sha256.New, []byte(signKey))
	h.Write([]byte(urlPath))
	h.Write([]byte(urlQuery))
	buf := h.Sum(nil)

	fmt.Println(urlPath + "?" + urlQuery + "&sign=" + base64.RawURLEncoding.EncodeToString(buf))
}

/*
➜  go run sign.go
/resize?nocrop=true&type=jpeg&url=https%3A%2F%2Fwww.google.com%2Flogos%2Fdoodles%2F2015%2Fgoogles-new-logo-5078286822539264.3-hp2x.gif&width=200&sign=9Rawdy5gEmqGTRgxUOO7fFMYegivSQd1jNSuJljY2PM
*/