recator: use timer signals instead of shared.Message.TimeLeft

- remove shared.Message.TimeLeft
- modify Timer struct
  - add TimeLeft signal
  - add End and Abort signals
- add syncronised ticker
- update RunPomodoro to use goroutines for timer starts
  - add waitForTimer function

internal/pomodoro/pomodoro.go

@@ -9,6 +9,19 @@ import (
 var mu sync.Mutex // to synchronize access to shared state
 var timer Timer
 
+func waitForTimer(t Timer) bool {
+	for {
+		select {
+		case <-t.End:
+			return true
+		case <-t.Abort:
+			return false
+		case shared.Message.TimeLeft = <-t.TimeLeft:
+			// do nothing, just let the timer update the message
+		}
+	}
+}
+
 // RunPomodoro iterates the Pomodoro work/break sessions.
 func RunPomodoro() {
 	mu.Lock()
@@ -24,18 +37,21 @@ func RunPomodoro() {
 		shared.Message.Session = session
 
 		shared.Message.Mode = "Work"
-		if !timer.Start(pomodoroConfig.Work) {
+		go timer.Start(pomodoroConfig.Work)
+		if !waitForTimer(timer) {
 			break
 		}
 
-		if session > pomodoroConfig.Sessions {
+		if session < pomodoroConfig.Sessions {
 			shared.Message.Mode = "ShortBreak"
-			if !timer.Start(pomodoroConfig.ShortBreak) {
+			go timer.Start(pomodoroConfig.ShortBreak)
+			if !waitForTimer(timer) {
 				break
 			}
 		} else { // last phase, prepare for finish
 			shared.Message.Mode = "LongBreak"
-			if !timer.Start(pomodoroConfig.LongBreak) {
+			go timer.Start(pomodoroConfig.LongBreak)
+			if !waitForTimer(timer) {
 				break
 			}
 			shared.Message.Mode = "End"