signature check for all requests

server.go

 //
 func apiV1Main(w http.ResponseWriter, r *http.Request) {
 	logRequestDebug(httputil.DumpRequest(r, true))
+	if checkSignature(r) == false {
+		fmt.Fprintf(w, "") //empty string
+		return
+	}
 
 	switch r.Method {
 	case "POST":