internal/lsp/source: document the handling of GOPRIVATE for linkTarget

Document that modules matching GOPRIVATE will not be linked.

Updates golang/vscode-go#2362

Change-Id: I7e2447bb50a2cd0d7d394f8589ccd4498f889048
Reviewed-on: https://go-review.googlesource.com/c/tools/+/419979
Run-TryBot: Robert Findley <[email protected]>
gopls-CI: kokoro <[email protected]>
Auto-Submit: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Hyang-Ah Hana Kim <[email protected]>

Author: findleyr

gopls/doc/settings.md

@@ -363,6 +363,9 @@ It might be one of:
 
 If company chooses to use its own `godoc.org`, its address can be used as well.
 
+Modules matching the GOPRIVATE environment variable will not have
+documentation links in hover.
+
 Default: `"pkg.go.dev"`.
 
 ##### **linksInHover** *bool*

internal/lsp/source/api_json.go

@@ -350,6 +350,9 @@ type DocumentationOptions struct {
 	// * `"pkg.go.dev"`
 	//
 	// If company chooses to use its own `godoc.org`, its address can be used as well.
+	//
+	// Modules matching the GOPRIVATE environment variable will not have
+	// documentation links in hover.
 	LinkTarget string
 
 	// LinksInHover toggles the presence of links to documentation in hover.