This change upgrades the deployment of tour to use the newer
Go 1.11 runtime. As part of that, the appengine build tag is
removed (it's no longer set by App Engine), and the GAE_ENV
environment variable is used to detect when tour is being run
in App Engine mode.
Set an environment variable in app.yaml to configure the
x/tools/godoc/golangorgenv package appropriately.
Factor out the static file handlers in local.go, but keep
static file handlers in app.yaml for improved latency across
global regions.
Updates golang/go#30486
Change-Id: Ia5bc88aab34fd07bf6ff0785da831180f509156f
Reviewed-on: https://go-review.googlesource.com/c/tour/+/165537
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
X-Tour-Commit: 45a20b0d69ef2b06d2edfd97210a0df9ffd7f829
Dmitri Shuralyov