docs/debugging.md: document lack of symlink support

This change documents the fact that this extension
does not support debugging symlinked projects.

Updates golang/vscode-go#622

Change-Id: Iffc3bfb0438a84cc3afbb6aadd00df040b83c14b
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/257204
Trust: Suzy Mueller <suzmue@golang.org>
Run-TryBot: Suzy Mueller <suzmue@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Polina Sokolova <polina@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/docs/debugging.md b/docs/debugging.md
index 23efb2d..61eabe3 100644
--- a/docs/debugging.md
+++ b/docs/debugging.md
@@ -373,6 +373,12 @@
 
 This error can show up for Mac users using Delve versions 0.12.2 and above. `xcode-select --install` has solved the problem for a number of users.
 
+### Debugging symlink directories
+
+This extension does not provide support for debugging projects containing symlinks. Make sure that you are setting breakpoints in the files that Go will use to compile your program.
+
+For updates to symlink support reference [golang/vscode-go#622](https://github.com/golang/vscode-go/issues/622).
+
 [Delve]: https://github.com/go-delve/delve
 [VS Code variables]: https://code.visualstudio.com/docs/editor/variables-reference
 [snippets]: https://code.visualstudio.com/docs/editor/userdefinedsnippets