Shuffle array

// Based on Fisher-Yates algorithm
func shuffleRecipients(shuffle []*data.Recipient) {
    rand.Seed(time.Now().UnixNano())
    for n := len(shuffle) - 1; n > 0; n-- {
        j := rand.Intn(n + 1)
        shuffle[n], shuffle[j] = shuffle[j], shuffle[n]
    }
}