Use quit channel.

main.go

@@ -9,7 +9,6 @@ import (
 	"os"
 	"path"
 	"strings"
-	"time"
 )
 
 var (
@@ -29,8 +28,9 @@ func main() {
 	defer file.Close()
 
 	c := make(chan string, *worker)
+	quit := make(chan bool)
 	for i := 0; i < *worker; i++ {
-		go processFileEntry(c)
+		go processFileEntry(c, quit)
 	}
 
 	scanner := bufio.NewScanner(file)
@@ -39,14 +39,16 @@ func main() {
 	}
 	close(c)
 
-	// Let's wait 10 sec for the last images to download.
-	time.Sleep(10 * 1e9)
+	for i := 0; i < *worker; i++ {
+		<-quit
+	}
 }
 
-func processFileEntry(c <-chan string) {
+func processFileEntry(c <-chan string, quit chan<- bool) {
 	for str := range c {
 		downloadFile(str)
 	}
+	quit <- true
 }
 
 func downloadFile(url string) {