docs: fix godoc README link

Change-Id: I6f70e2bdb7f5d8607a99252001068c3e83a89f9f
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/46930
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jean de Klerk <deklerk@google.com>
diff --git a/README.md b/README.md
index 2a66eef..dc1ae92 100644
--- a/README.md
+++ b/README.md
@@ -77,7 +77,7 @@
 > **Stable status**: the API is mature and ready for production use. We will
 > continue addressing bugs and feature requests.
 
-Documentation and examples are available at [godoc.org/cloud.google.com/go](godoc.org/cloud.google.com/go)
+Documentation and examples are available at [godoc.org/cloud.google.com/go](https://godoc.org/cloud.google.com/go)
 
 ## Go Versions Supported