gddo-server: make GDDO_TEE_REQUESTS_TO_PKGGODEV case insensitive

Change-Id: I0dbde3213cee1e29631a5e68fee75e396c2253e4
Reviewed-on: https://go-review.googlesource.com/c/gddo/+/277853
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/gddo-server/main.go b/gddo-server/main.go
index f34fc0f..5cf992e 100644
--- a/gddo-server/main.go
+++ b/gddo-server/main.go
@@ -1079,7 +1079,7 @@
 		log.Printf("teeRequestToPkgGoDev(%q): not teeing request", r.URL.Path)
 		return
 	}
-	if os.Getenv("GDDO_TEE_REQUESTS_TO_PKGGODEV") == "true" {
+	if strings.ToLower(os.Getenv("GDDO_TEE_REQUESTS_TO_PKGGODEV")) == "true" {
 		gddoEvent, pkggodevEvent := teeRequestToPkgGoDev(r, latency, s.isRobot(r), status)
 		payload := map[string]interface{}{
 			"godoc.org":  gddoEvent,