[golangci-lint]: Use stronger random number generator for rPad.

helpers.go

@@ -6,9 +6,10 @@ package main
 
 import (
 	"bytes"
+	"crypto/rand"
 	"fmt"
 	"log"
-	"math/rand"
+	"math/big"
 	"net/url"
 	"os"
 	"regexp"
@@ -50,9 +51,14 @@ func readFile(path string) (*bytes.Buffer, error) {
 func getRpad(messageLength int) string {
 	rpadRunes := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
 	length := 100 - messageLength%100
+	max := big.NewInt(int64(len(rpadRunes)))
 	rpad := make([]rune, length)
 	for i := range rpad {
-		rpad[i] = rpadRunes[rand.Intn(len(rpadRunes))]
+		randInt, err := rand.Int(rand.Reader, max)
+		if err != nil {
+			log.Fatal(err)
+		}
+		rpad[i] = rpadRunes[randInt.Int64()]
 	}
 	return string(rpad)
 }