add: --timeout option in watch command

cmd_wait.go

@@ -1,7 +1,10 @@
 package main
 
 import (
+	"context"
 	"errors"
+	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -13,6 +16,7 @@ type waitCmd struct {
 
 	Closed    bool         `help:"wait until the window is closed"`
 	Intervals gli.Duration `cli:"intervals,i=DURATION" default:"1s"`
+	Timeout   gli.Duration `cli:"timeout=DURATION" default:"0s" help:"zelo value means ininite"`
 }
 
 func (c waitCmd) Run(args []string) error {
@@ -23,6 +27,14 @@ func (c waitCmd) Run(args []string) error {
 	an := ancestors()
 	t := strings.ToLower(args[0])
 
+	var ctx context.Context
+	if c.Timeout == 0 {
+		ctx = context.Background()
+	} else {
+		ctx, _ = context.WithTimeout(context.Background(), c.Timeout.Duration())
+	}
+
+waitLoop:
 	for {
 		wins, err := listAllWindows()
 		if err != nil {
@@ -40,6 +52,14 @@ func (c waitCmd) Run(args []string) error {
 			}
 		}
 
+		select {
+		case <-ctx.Done():
+			fmt.Fprintln(os.Stderr, "cancelled")
+			break waitLoop
+		default:
+			//nop
+		}
+
 		time.Sleep(c.Intervals.Duration())
 	}