app: use factored import in default snippet

This is a slightly more convenient starting point when adopting this
snippet for your own needs.

Fixes golang/go#13813

Change-Id: I0ece3d811d77c82121a90f52823b69b35f4a6e2c
Reviewed-on: https://go-review.googlesource.com/18189
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

app/goplay/edit.go

diff --git a/app/goplay/edit.go b/app/goplay/edit.go
index d0fb6e1..ce29a78 100644
--- a/app/goplay/edit.go
+++ b/app/goplay/edit.go
@@ -66,7 +66,9 @@
 
 const hello = `package main
 
-import "fmt"
+import (
+	"fmt"
+)
 
 func main() {
 	fmt.Println("Hello, playground")