randomstring fix

@@ -39,13 +39,20 @@ func AssertJson(object interface{})string{
 
 var randomChars = "ABCDEFGHJKMNPQRSTWXYZabcdefhjkmnprstwxyz2345678" /****默认去掉了容易混淆的字符oOLl,9gq,Vv,Uu,I1****/
 func RandomString(l int)string{
+	return RandomStringWithChars(l,randomChars)
+}
+
+func RandomStringWithChars(l int,chars string)string{
 	if l<=0{
 		return ""
 	}
-	lenChars :=len(randomChars) -1
+	if len(chars)==0{
+		return ""
+	}
+	lenChars :=len(chars) -1
 	rsp :=bytes.NewBuffer(nil)
 	for i:=0;i<l;i++{
-		rsp.WriteByte(randomChars[rand.Intn(lenChars)])
+		rsp.WriteByte(chars[rand.Intn(lenChars)])
 	}
 	return rsp.String()
 }
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