我无法在 Ubuntu 16.04 中安装 snap，而是收到如下所示的错误：
dheer@dheer-Inspiron-3558:~$ sudo snap install notes
[sudo] password for dheer: *********
error: cannot perform the following tasks:
- Fetch and check assertions for snap "ubuntu-core" (423) (Get https://assertions.ubuntu.com/v1/assertions/snap-revision/7sS9MbzjeZ87E4IVq3ByrAO8t1YqriNlaX4r7eT5AHYZjzRCa7twTmWU53e6falH: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers))
dheer@dheer-Inspiron-3558:~$
请帮忙？