Support alphanumeric in RandString

pkg/utils/strings.go

@@ -15,7 +15,7 @@ package utils
 
 import "math/rand"
 
-var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
 
 func RandStringRunes(n int) string {
 	b := make([]rune, n)