I'm planning to write a Visual Studio Code extension and it need to save some information for example a counter. The user can press a shortcut to increase or decrease the counter and the value of the counter will be saved some where. Next time when the user starts Visual Studio Code, the extension can load the counter's last value. My question is, where is the proper place to store this info?
You're probably looking for the Memento API. The ExtensionContext has two different memento instances you can access:
workspaceState
A memento object that stores state in the context of the currently opened workspace.
globalState
A memento object that stores state independent of the current opened workspace.
Both survive VSCode updates to my knowledge.