add support for automatically unloading a model (#10) (#14)

* Make starting upstream process on-demand (#10)
* Add automatic unload of model after TTL is reached
* add `ttl` configuration parameter to models in seconds, default is 0 (never unload)

misc/simple-responder/simple-responder.go

@@ -20,7 +20,11 @@ func main() {
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		// Set the header to text/plain
 		w.Header().Set("Content-Type", "text/plain")
+		fmt.Fprintln(w, *responseMessage)
+	})
 
+	http.HandleFunc("/env", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/plain")
 		fmt.Fprintln(w, *responseMessage)
 
 		// Get environment variables