playground: display the version of Go in use

Fixes golang/go#12218

Change-Id: Ie8bdfdecdeb5b7a61eaa742b86612afef704c2fe
Reviewed-on: https://go-review.googlesource.com/98446
Reviewed-by: Andrew Bonventre <andybons@golang.org>
diff --git a/edit.go b/edit.go
index bb5eaa3..b69c1c0 100644
--- a/edit.go
+++ b/edit.go
@@ -8,6 +8,7 @@
 	"fmt"
 	"html/template"
 	"net/http"
+	"runtime"
 	"strings"
 
 	"cloud.google.com/go/datastore"
@@ -21,6 +22,7 @@
 	Snippet   *snippet
 	Share     bool
 	Analytics bool
+	GoVersion string
 }
 
 func (s *server) handleEdit(w http.ResponseWriter, r *http.Request) {
@@ -67,6 +69,7 @@
 		Snippet:   snip,
 		Share:     allowShare(r),
 		Analytics: r.Host == hostname,
+		GoVersion: runtime.Version(),
 	}
 	if err := editTemplate.Execute(w, data); err != nil {
 		s.log.Errorf("editTemplate.Execute(w, %+v): %v", data, err)
diff --git a/edit.html b/edit.html
index 8bf62f2..0be1443 100644
--- a/edit.html
+++ b/edit.html
@@ -170,7 +170,7 @@
 
 <p>
 The playground uses the latest stable release of Go.<br>
-To find the precise version, run <a href="/p/1VcPUlPk_3">this program</a>.
+The current version is <a href="/p/1VcPUlPk_3">{{.GoVersion}}</a>.
 </p>
 
 <p>