Go math/rand.NewZipf example

main.go

package main

import (
	"fmt"
	"log"
	"math/rand"
	"sort"
	"time"
)

func main() {
	if err := run(); err != nil {
		log.Fatal(err)
	}
}

func run() error {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	z := rand.NewZipf(r, 3, 10, 100)

	counts := make(map[int]int)
	for i := 0; i < 1000; i++ {
		j := z.Uint64()
		counts[int(j)]++
	}

	keys := make([]int, 0, len(counts))
	for key := range counts {
		keys = append(keys, key)
	}
	sort.Ints(keys)

	for _, key := range keys {
		fmt.Printf("%d: %d\n", key, counts[key])
	}
	fmt.Printf("len(keys)=%d\n", len(keys))
	return nil
}

https://play.golang.org/p/dT7vXT_Vjc0