from: http://marcio.io/2015/07/calculating-multiple-file-hashes-in-a-single-pass/

main.go

package main

import (
	"bufio"
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"encoding/hex"
	"fmt"
	"io"
	"log"
	"os"
	"runtime"
)

func main() {
	args := os.Args[1:]

	var filename string
	filename = args[0]

    // open an io.Reader from the file we would like to calculate hashes
	f, err := os.OpenFile(filename, os.O_RDONLY, 0)
	if err != nil {
		log.Fatalln("Cannot open file: %s", filename)
	}
	defer f.Close()

	info := CalculateBasicHashes(f)

	fmt.Println("md5    :", info.Md5)
	fmt.Println("sha1   :", info.Sha1)
	fmt.Println("sha256 :", info.Sha256)
	fmt.Println("sha512 :", info.Sha512)
	fmt.Println()
}