Updated RandomString function with a very efficient variant

tools.go

@@ -2,16 +2,17 @@ package toolkit
 
 import (
 	"bytes"
-	"crypto/rand"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
+	"math/rand"
 	"net/http"
 	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
+	"time"
 )
 
 const randomStringSource = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_+"
@@ -28,14 +29,14 @@ type Tools struct {
 // RandomString returns a string of random characters of length n, using randomStringSource
 // as the source for the string
 func (t *Tools) RandomString(n int) string {
-	s, r := make([]rune, n), []rune(randomStringSource)
-	for i := range s {
-		p, _ := rand.Prime(rand.Reader, len(r))
-		x, y := p.Uint64(), uint64(len(r))
-		s[i] = r[x%y]
+	rand.Seed(time.Now().UnixNano())
+	sb := strings.Builder{}
+	sb.Grow(n)
+	for i := 0; i < n; i++ {
+		sb.WriteByte(randomStringSource[rand.Intn(len(randomStringSource))])
 	}
 
-	return string(s)
+	return sb.String()
 }
 
 // UploadedFile is a struct used to save information about an uploaded file