Send EOT before exiting

The processes were left behind when clients closed their windows.

app/app.go

@@ -201,6 +201,7 @@ func (app *App) generateHandler() func(w http.ResponseWriter, r *http.Request) {
 
 		go func() {
 			<-exit
+			fio.Write([]byte{4})
 			fio.Close()
 			conn.Close()
 			log.Printf("Connection closed: %s", r.RemoteAddr)