make random files in go of various sizes

go_file_maker.go

package main

import (
	"fmt"
	"io/ioutil"
	"math/rand"
	"time"
)

var (
	sizes   = []int{100000, 1000000, 1000000, 2000000, 5000000, 10000000, 50000000, 100000000}
	runeset = []rune("-0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
)

func main() {

	for _, size := range sizes {
		fn := fmt.Sprintf("sample_file_%d.txt", size)
		token := fmt.Sprintf("sl.")
		size_prefix := fmt.Sprintf("xXxXx-%d-xXxXx", size)
		token += size_prefix

		token += RandomStringFromRuneset(size-len(size_prefix), runeset)
		file := fmt.Sprintf("token_size: %d\ntoken: %s\nanother_field: value\n", size, token)

		if err := ioutil.WriteFile(fn, []byte(file), 0644); err != nil {
			panic(err)
		}
	}

}

func RandomStringFromRuneset(length int, runeset []rune) string {
	runes := make([]rune, length)
	runeset_size := len(runeset)
	rand.Seed(time.Now().UTC().UnixNano())
	for i := range runes {
		runes[i] = runeset[rand.Intn(runeset_size)]
	}
	return string(runes)
}