Chap19 738 (#740)

* fix http response content-type error

* fix_chap19_739

eBook/examples/chapter_19/goto_v1/main.go

@@ -33,6 +33,7 @@ func Redirect(w http.ResponseWriter, r *http.Request) {
 func Add(w http.ResponseWriter, r *http.Request) {
 	url := r.FormValue("url")
 	if url == "" {
+		w.Header().Set("Content-Type", "text/html")
 		fmt.Fprint(w, AddForm)
 		return
 	}

eBook/examples/chapter_19/goto_v5/store.go

@@ -64,7 +64,7 @@ func (s *URLStore) Set(key, url *string) error {
 	return nil
 }
 
-func (s *URLStore) Count() int {
+func (s *URLStore) count() int {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 	return len(s.urls)
@@ -72,7 +72,7 @@ func (s *URLStore) Count() int {
 
 func (s *URLStore) Put(url, key *string) error {
 	for {
-		*key = genKey(s.Count())
+		*key = genKey(s.count())
 		if err := s.Set(key, url); err == nil {
 			break
 		}