Allow specifying a time to count down to

The input for this is dumb AF, but it "works".  Added flags are:
-target-year
-target-month
-target-day
-target-hour
-target-minute
-target-second

These flags all take a number, and default to the current time if
omitted.

main.go

@@ -28,29 +28,71 @@ func main() {
 	var format string
 
 	flag.StringVar(&filename, "o", "/tmp/countdown.txt", "Output file to write the countdown to.")
-	flag.StringVar(&untilStr, "u", "10m", "Countdown duration")
+	flag.StringVar(&untilStr, "u", "", "Countdown duration")
 	flag.StringVar(&targetTimeStr, "t", "", "Countdown to time")
 	flag.StringVar(&doneStr, "d", "00:00:00", "String to display when done")
 	//flag.StringVar(&format, "f", "%H:%M:%S", "Format for the countdown")
 	flag.StringVar(&format, "f", "{{if .Hours}}{{.Hours}}h {{end}}{{if or .Minutes .Hours}}{{.Minutes}}m {{end}}{{.Seconds}}s", "Format for the countdown")
+
+	var targetYear int
+	var targetDay int
+	var targetMonth int
+
+	flag.IntVar(&targetYear, "target-year", -1, "")
+	flag.IntVar(&targetDay, "target-day", -1, "")
+	flag.IntVar(&targetMonth, "target-month", -1, "")
+
+	var targetHour int
+	var targetMinute int
+	var targetSecond int
+
+	flag.IntVar(&targetHour, "target-hour", -1, "")
+	flag.IntVar(&targetMinute, "target-minute", -1, "")
+	flag.IntVar(&targetSecond, "target-second", -1, "")
+
 	flag.Parse()
 
-	untilDuration, err := time.ParseDuration(untilStr)
+	var until time.Time
-	if err != nil {
+	now := time.Now()
-		fmt.Println(err)
+
-		os.Exit(1)
+	if untilStr != "" {
+		untilDuration, err := time.ParseDuration(untilStr)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		until = time.Now().Add(untilDuration)
+	} else {
+		if targetYear == -1 {
+			targetYear = now.Year()
+		}
+		if targetMonth == -1 {
+			targetMonth = int(now.Month())
+		}
+		if targetDay == -1 {
+			targetDay = now.Day()
+		}
+
+		if targetHour == -1 {
+			targetHour = now.Hour()
+		}
+		if targetMinute == -1 {
+			targetMinute = now.Minute()
+		}
+		if targetSecond == -1 {
+			targetSecond = now.Second()
+		}
+
+		until = time.Date(
+			targetYear, time.Month(targetMonth), targetDay,
+			targetHour, targetMinute, targetSecond,
+			0, time.Local,
+		)
 	}
 
-	var until time.Time = time.Now().Add(untilDuration)
+	fmt.Printf("Output file: %s\nCountdown to: %s\n", filename, untiluntil)
-
-	d, err := time.ParseDuration("1s")
-	if err != nil {
-		fmt.Println(err)
-		os.Exit(1)
-	}
-
-	fmt.Printf("Output file: %s\nCountdown duration: %s\n", filename, untilDuration)
 
+	var err error
 	tp := template.New("time")
 	tp, err = tp.Parse(format)
 	if err != nil {
@@ -60,9 +102,11 @@ func main() {
 
 	wg := sync.WaitGroup{}
 	wg.Add(1)
-	ticker := time.NewTicker(d)
+	ticker := time.NewTicker(time.Second)
+
 	go func(c <-chan time.Time) {
 		count := time.Until(until)
+		fmt.Println(count)
 		for ; count >= 0; count = time.Until(until) {
 			h := int(count.Hours())
 			m := int(int(count.Minutes()) % 60)