doc/effective_go: fix broken link

Change-Id: I99b9be77dd665be634cf49a834bc0f82e9cce45e
GitHub-Last-Rev: 5d01712aae
GitHub-Pull-Request: golang/website#257
Reviewed-on: https://go-review.googlesource.com/c/website/+/535495
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

_content/doc/effective_go.html

@@ -63,7 +63,7 @@ use the language.
 Moreover, many of the packages contain working, self-contained
 executable examples you can run directly from the
 <a href="https://golang.org">golang.org</a> web site, such as
-<a href="/pkg/strings/#example_Map">this one</a> (if
+<a href="/pkg/strings/#example-Map">this one</a> (if
 necessary, click on the word "Example" to open it up).
 If you have a question about how to approach a problem or how something
 might be implemented, the documentation, code and examples in the