internal/config: add GO_DISCOVERY_QUEUE_SERVICE

GO_DISCOVERY_QUEUE_SERVICE is added, which is used to determine which
service the tasks queue should send requests to.

Change-Id: I27d29ef9ffcd26a5c45412d5a4bb7832348f219d
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/239917
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/internal/config/config.go b/internal/config/config.go
index 9f5ca64..cec128a 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -70,6 +70,10 @@
 	// AppEngine identifiers
 	ProjectID, ServiceID, VersionID, ZoneID, InstanceID, LocationID string
 
+	// QueueService is used to identify which service Cloud Tasks queue
+	// should send requests to.
+	QueueService string
+
 	GaeEnv string
 
 	// AppMonitoredResource is the resource for the current GAE app.
@@ -213,11 +217,12 @@
 		Port:      os.Getenv("PORT"),
 		DebugPort: os.Getenv("DEBUG_PORT"),
 		// Resolve AppEngine identifiers
-		ProjectID:  os.Getenv("GOOGLE_CLOUD_PROJECT"),
-		ServiceID:  os.Getenv("GAE_SERVICE"),
-		VersionID:  os.Getenv("GAE_VERSION"),
-		InstanceID: os.Getenv("GAE_INSTANCE"),
-		GaeEnv:     os.Getenv("GAE_ENV"),
+		ProjectID:    os.Getenv("GOOGLE_CLOUD_PROJECT"),
+		ServiceID:    os.Getenv("GAE_SERVICE"),
+		VersionID:    os.Getenv("GAE_VERSION"),
+		InstanceID:   os.Getenv("GAE_INSTANCE"),
+		GaeEnv:       os.Getenv("GAE_ENV"),
+		QueueService: os.Getenv("GO_DISCOVERY_QUEUE_SERVICE"),
 		// LocationID is essentially hard-coded until we figure out a good way to
 		// determine it programmatically, but we check an environment variable in
 		// case it needs to be overridden.
diff --git a/internal/queue/queue.go b/internal/queue/queue.go
index cc13d9f..a66365a 100644
--- a/internal/queue/queue.go
+++ b/internal/queue/queue.go
@@ -10,7 +10,6 @@
 	"context"
 	"crypto/sha256"
 	"fmt"
-	"os"
 	"time"
 
 	cloudtasks "cloud.google.com/go/cloudtasks/apiv2"
@@ -71,7 +70,7 @@
 					HttpMethod:  taskspb.HttpMethod_POST,
 					RelativeUri: u,
 					AppEngineRouting: &taskspb.AppEngineRouting{
-						Service: os.Getenv("GAE_SERVICE"),
+						Service: q.cfg.QueueService,
 					},
 				},
 			},