cmd/golangorg: default to go.dev for testing server

When running server locally, requests for /foo redirect
to /golang.org/foo, and you can specify other hosts at the
start of the URL instead.

Preparing for the move to go.dev, redirect /foo to /go.dev/foo instead.
This just makes local development and testing a little nicer.
It doesn't have any effect on the actual server.

Change-Id: Iabc4186559cbf498f9b361060412702153859a6d
Reviewed-on: https://go-review.googlesource.com/c/website/+/362958
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Jamal Carvalho <jamal@golang.org>

cmd/golangorg/server.go

@@ -399,11 +399,11 @@ var validHosts = map[string]bool{
 func hostEnforcerHandler(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		isHTTPS := r.TLS != nil || r.Header.Get("X-Forwarded-Proto") == "https" || r.URL.Scheme == "https"
-		defaultHost := "golang.org"
+		defaultHost := "go.dev"
 		host := strings.ToLower(r.Host)
 		isValidHost := validHosts[host]
 
-		if googleCN(r) && strings.HasSuffix(host, "golang.org") {
+		if googleCN(r) && !strings.HasSuffix(host, "google.cn") {
 			// golang.google.cn is the only web site in China.
 			defaultHost = "golang.google.cn"
 			isValidHost = strings.ToLower(r.Host) == defaultHost
@@ -441,7 +441,7 @@ func hostPathHandler(h http.Handler) http.Handler {
 			elem, rest = elem[:i], elem[i+1:]
 		}
 		if !validHosts[elem] {
-			u := "/golang.org" + r.URL.EscapedPath()
+			u := "/go.dev" + r.URL.EscapedPath()
 			if r.URL.RawQuery != "" {
 				u += "?" + r.URL.RawQuery
 			}

cmd/golangorg/testdata/web.txt

@@ -3,7 +3,7 @@ code == 301
 redirect == https://go.dev/
 
 GET http://localhost:6060/
-redirect == /golang.org/
+redirect == /go.dev/
 
 GET http://localhost:6060/go.dev/
 body contains Go is an open source programming language