golang 断言类型，否则panic

当遇到 interface{}，一档要处理，否则就会有 panic

for _, v := range countList {
			var key uint64
			switch val := v["parent_id"].(type) {
			case uint64:
				key = val
			case int64:
				key = uint64(val)
			case float64:
				key = uint64(val)
			case string:
				parsed, err := strconv.ParseUint(val, 10, 64)
				if err != nil {
					continue
				}
				key = parsed
			default:
				// 类型不支持，跳过
				continue
			}
		}