fix poll/send race condition and panic on errors instead of ignoring

command.go

@@ -38,6 +38,10 @@ func (app *App) Poll(since int) (num int, err error) {
 }
 
 func (app *App) Last(n int) (err error) {
+	if n == 0 {
+		return nil
+	}
+
 	if _, err := fmt.Fprintf(app.conn, "LAST %d\n", n); err != nil {
 		return err
 	}
@@ -52,6 +56,10 @@ func (app *App) Last(n int) (err error) {
 		return err
 	}
 
+	if nsrv == 0 {
+		goto count
+	}
+
 	for range nsrv {
 		if !app.scanner.Scan() {
 			return app.scanner.Err()
@@ -59,6 +67,7 @@ func (app *App) Last(n int) (err error) {
 		app.incoming <- Message(app.scanner.Text())
 	}
 
+count:
 	var last int
 	if !app.scanner.Scan() {
 		return app.scanner.Err()

event.go

@@ -4,25 +4,37 @@ type IncomingEvent interface {
 	HandleIncoming(*App)
 }
 type OutgoingEvent interface {
-	HandleOutgoing(*App)
+	HandleOutgoing(*App) error
 }
 
 type Message string
 
 func (m Message) HandleIncoming(app *App) {
 	app.AppendMessage(string(m))
+
+}
+func (m Message) HandleOutgoing(app *App) error {
+	num, err := app.Send(string(m))
+	if err != nil {
+		return err
 	}
-func (m Message) HandleOutgoing(app *App) {
-	num, _ := app.Send(string(m))
 	app.incoming <- SetLast(num)
 
+	return nil
 }
 
 type Poll int
 
-func (p Poll) HandleOutgoing(app *App) {
-	num, _ := app.Poll(int(p))
-	go app.Last(num)
+func (p Poll) HandleOutgoing(app *App) error {
+	num, err := app.Poll(int(p))
+	if err != nil {
+		return err
+	}
+	err = app.Last(num)
+	if err != nil {
+		return err
+	}
+	return nil
 }
 
 type SetLast int

main.go

@@ -59,6 +59,7 @@ type App struct {
 
 	incoming chan IncomingEvent
 	outgoing chan OutgoingEvent
+	error    chan error
 
 	vx *vaxis.Vaxis
 	w  struct {
@@ -82,14 +83,18 @@ func (app *App) Connect(host, port string) (err error) {
 	app.scanner = bufio.NewScanner(app.conn)
 	app.incoming = make(chan IncomingEvent)
 	app.outgoing = make(chan OutgoingEvent)
-	app.ticker = time.NewTicker(2 * time.Second)
+	app.error = make(chan error)
+	app.ticker = time.NewTicker(1 * time.Second)
 
 	go func() {
 		app.Last(50)
 		for {
 			select {
 			case ev := <-app.outgoing:
-				ev.HandleOutgoing(app)
+				if err := ev.HandleOutgoing(app); err != nil {
+					app.error <- err
+					return
+				}
 			case <-app.ctx.Done():
 				return
 			}
@@ -179,6 +184,9 @@ func main() {
 			ev.HandleIncoming(&app)
 		case <-app.ticker.C:
 			app.outgoing <- Poll(app.last)
+		case err := <-app.error:
+			app.FinishUI()
+			panic(err)
 		case <-app.ctx.Done():
 			return
 		}