https://code.visualstudio.com/blogs/2017/02/12/code-lens-roundup
https://marketplace.visualstudio.com/items?itemName=abierbaum.vscode-file-peek
https://github.com/xxMUROxx/vscode.code_call_lens/blob/master/src/extension.ts
https://code.visualstudio.com/docs/extensionAPI/language-support#_codelens-show-actionable-context-information-within-source-code
https://marketplace.visualstudio.com/items?itemName=waderyan.code-lens-roundup
github有許多開源項目，可以在上面找相關項目參考。