This change replaces the env package with a new golangorgenv package.

The previous env package existed primarily to configure the godoc
instance that was running golang.org. By now, the golang.org website
has been factored out to x/website, which has its own env package,
but ends up still using this env package indirectly via x/tools/godoc.

The goal of this change is to make env available for other services
that run on subdomains of golang.org, so they can continue to safely
rely on the x/tools/playground, which will be modified in the next
commit to also use the new golangorgenv.

The golangorgenv package replaces the IsProd function with a more
specific one. Start using it in packages x/tools/{,cmd}/godoc. Also,
re-arrange the order of checks to give the host suffix check higher
priority than the environment variable check. This way, if the
environment variable isn't set, the host suffix check gets a chance
to run.

When getting the value of "X-AppEngine-Country" header, use its
canonical format "X-Appengine-Country" to avoid an allocation.
This does not change behavior.

Updates golang/go#30486

Change-Id: I97b47211a45ca0351f31fcb4fa6d408a4b0c4c7c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/165459
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

With modern versions of App Engine, it's no longer needed to use the
google.golang.org/appengine/... packages.

Package log from standard library can be used instead of the
google.golang.org/appengine/log package. Packages net/http and
context from standard library can be used instead of
google.golang.org/appengine/urlfetch.

This simplifies the code and reduces the number of dependences.

Start using the golangorgenv package from previous commit to
make the decision of whether to enforce sharing restrictions,
rather than relying on the appengine build tag. The appengine
build tag is no longer set in App Engine Standard with Go 1.11+
runtime. An alternative solution would be detect App Engine by
doing something like:

	// GAE_ENV environment variable is set to "standard" in App Engine environment, Go 1.11 runtime.
	// See https://cloud.google.com/appengine/docs/standard/go111/runtime#environment_variables.
	var onAppengine = os.Getenv("GAE_ENV") == "standard"

But we choose to upgrade to explicit app-scoped environment variable
configuration as part of this change. It provides better security
properties, and the value of adding an intermediate transitional step
is not high enough to justify doing it.

When getting the value of "X-AppEngine-Country" header, use its
canonical format "X-Appengine-Country" to avoid an allocation.
This does not change behavior.

Run go mod tidy (using Go 1.12).

Updates golang/go#29981
Updates golang/go#30486

Change-Id: I82a59e0f28623e06762b7ebdf3930b5ee243acda
Reviewed-on: https://go-review.googlesource.com/c/tools/+/160837
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This uses the new golangorgenv package from CL 165459 to enable
country check in the /share endpoint registered by x/tools/playground
package. This improves consistency with other similar services that
also use the x/tools/playground package.

Updates golang/go#30486

Change-Id: Idc6db4e384a7392aa39967f3320c2158a9c7e99a
Reviewed-on: https://go-review.googlesource.com/c/talks/+/165742
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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>

This change upgrades the deployment of blog 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 blog is being run
in App Engine mode.

Set an environment variable in app.yaml to configure the
x/tools/godoc/golangorgenv package appropriately.

Modify the static file server to also serve /favicon.ico,
but keep static file handlers in app.yaml for improved latency
across global regions.

Updates golang/go#30486

Change-Id: I63ca78a075d94d43a40f0b963b5f6d0d8270c34e
Reviewed-on: https://go-review.googlesource.com/c/blog/+/165460
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>