This generate a dovecot password in golang, inspired by https://gist.github.com/garrettreid/8329796

doveadmpw.go

package main

import (
	"crypto/sha512"
	"encoding/base64"
	"fmt"
	"math/rand"
	"time"
)

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

var src = rand.NewSource(time.Now().UnixNano())

//http://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-golang
func RandStringBytesMaskImprSrc(n int) string {
	b := make([]byte, n)
	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}

	return string(b)
}
func main() {
	salt := RandStringBytesMaskImprSrc(5)
	password := "randompass"
	hasher := sha512.New()
	hasher.Write([]byte(password))
	hasher.Write([]byte(salt))
	fmt.Printf("{SSHA512}%s\n", base64.StdEncoding.EncodeToString([]byte(string(hasher.Sum(nil))+salt)))
}