Added lost error page

main.go

@@ -125,11 +125,16 @@ func (s *Server) FormPage(w http.ResponseWriter, r *http.Request) {
 	formTemplate.Execute(w, config)
 }
 
+func (s *Server) ErrorPage(w http.ResponseWriter, r *http.Request) {
+	errorTemplate.Execute(w, config)
+}
+
 func main() {
 	var io FsIo
 	server := Server{Io: &io}
 	http.HandleFunc(RequestStatusUrlPrefix, server.RequestPage)
 	http.HandleFunc(FormPostUrl, server.FormPostHandler)
 	http.HandleFunc(FormUrl, server.FormPage)
+	http.HandleFunc(ErrorUrl, server.ErrorPage)
 	log.Fatal(http.ListenAndServe("localhost:5678", nil))
 }

templates.go

@@ -18,6 +18,12 @@ var statusTemplate = template.Must(footer.New("status").Parse(`
 Status: {{ .Status }}
 {{ template "footer" .Global }}`))
 
+var errorTemplate = template.Must(footer.New("error").Parse(`
+{{ template "header" . }}
+<p>Error, all form fields must be field.</p>
+<a href="/">take ma back</a>
+{{ template "footer" . }}`))
+
 var formTemplate = template.Must(header.New("form").Parse(`{{ template "header" . }}
 <h1>~🐱 Sign up form</h1>
 <form action="/post" method="post">