Auto-open merged pdf also in Linux

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

.gitignore

@@ -25,3 +25,7 @@ _testmain.go
 .settings
 *.code-workspace
 .vscode
+
+# bin dir
+bin
+bin/*

fattureSanRossore.go

@@ -174,15 +174,18 @@ func mergeInvoices(files []string) string {
 }
 
 func openPDF(fileName string) {
+	var cmd *exec.Cmd
 	if runtime.GOOS == "windows" {
-		cmd := exec.Command("cmd", "/C start "+fileName)
+		cmd = exec.Command("cmd", "/C start "+fileName)
+
+	} else {
+		cmd = exec.Command("xdg-open", fileName)
+	}
 	err := cmd.Run()
 	if err != nil {
 		log.Fatalf("Impossibile aprire il pdf con le fatture unite: %v\n", err)
 	}
 }
-	//TODO for Linux
-}
 
 func main() {
 	var fileName string