feat: Add max concurrency option

src/get.go

@@ -44,8 +44,9 @@ func (e *strategyEnum) Type() string {
 
 // Command stuff
 var getFlags struct {
-	inputFile string
-	strategy  strategyEnum
+	inputFile      string
+	strategy       strategyEnum
+	maxConcurrency int64
 }
 
 var getCommand = &cobra.Command{
@@ -172,16 +173,42 @@ var getCommand = &cobra.Command{
 		// Handle downloading
 		switch getFlags.strategy {
 		case strategyConcurrent:
-			fmt.Println("Downloading concurrently...")
-
 			var waitGroup sync.WaitGroup
-			waitGroup.Add(len(argSet))
 
-			for url := range argSet {
-				go func(url string) {
-					defer waitGroup.Done()
-					downloadFile(url)
-				}(url)
+			// Concurrency with no limit
+			if getFlags.maxConcurrency == 0 {
+				fmt.Println("Downloading concurrently... [No limit]")
+				waitGroup.Add(len(argSet))
+
+				for url := range argSet {
+					go func(url string) {
+						defer waitGroup.Done()
+						downloadFile(url)
+					}(url)
+				}
+
+				// Concurrency with limit
+			} else {
+				fmt.Printf("Downloading concurrently... [Max: %d]\n", getFlags.maxConcurrency)
+				waitGroup.Add(int(getFlags.maxConcurrency))
+
+				// Establish channel and workers
+				ch := make(chan string)
+				for t := 0; t < int(getFlags.maxConcurrency); t++ {
+					go func() {
+						for url := range ch {
+							downloadFile(url)
+						}
+
+						waitGroup.Done()
+					}()
+				}
+
+				for url := range argSet {
+					ch <- url
+				}
+
+				close(ch)
 			}
 
 			waitGroup.Wait()
@@ -200,6 +227,7 @@ func init() {
 
 	rootCommand.AddCommand(getCommand)
 	getCommand.Flags().StringVarP(&getFlags.inputFile, "file", "f", "", "Path to the input file containing the url(s)")
+	getCommand.Flags().Int64VarP(&getFlags.maxConcurrency, "max-concurrency", "m", 10, "Maximum number of concurrent downloads [0 = unlimited] (default is 10)")
 	getCommand.Flags().VarP(&getFlags.strategy, "strategy", "s", "Strategy to use when downloading (default is concurrent)")
 	if err := getCommand.RegisterFlagCompletionFunc("strategy", strategyCompletion); err != nil {
 		fmt.Println("Failed to register completion for flag -s in get command")