Open file in corresponding workspace

It took me some time to understand why autocomplete does not work properly.

See https://stackoverflow.com/a/72743549/633961

I guess you want a different wording. Feel free to change the text of my PR. But I think
a hint like this needs to be at the top of the file.

docs/troubleshooting.md

@@ -8,6 +8,11 @@ If you suspect that the Go extension is not working correctly, please follow the
 
 Verify that your project is in good shape by working with it at the command line. Running a command like `go build ./...` in the workspace directory will compile everything. For modules, `go mod tidy` is another good check, though it may modify your `go.mod`.
 
+## Open file in corresponding workspace
+
+Make sure the you edit belongs to your module. If you open a file from a different module, then autocomplete might not work. Use "Open Folder" 
+to open a different go module.
+
 ## Look for serious errors and diagnostics
 
 Check that there aren't any diagnostics that indicate a problem with your workspace. First, check the bottom-center of the VS Code window for any errors. After that, check the package declaration of the any Go files you're working in, and your `go.mod` file. Problems in the workspace configuration can cause many different symptoms. See the [`gopls` workspace setup instructions](https://github.com/golang/tools/blob/master/gopls/doc/workspace.md) for help.
@@ -75,4 +80,4 @@ We can't diagnose a problem from just a description. When filing an issue, pleas
 1. Relevant VS Code settings: run `Preferences: Open Settings (JSON)` and include anything in a `[go]` block, and anything that starts with `go.` or `gopls.`
 1. Extension and `gopls` logs as seems appropriate for the bug. (Include from the beginning of the logs if possible.)
 
-Once you've collected that information, [file your issue](https://github.com/golang/vscode-go/issues/new/choose).
+Once you've collected that information, [file your issue](https://github.com/golang/vscode-go/issues/new/choose).