Rework batch package

Use a buffered channel to limit the number of active goroutines without needing
to wait for all active goroutines to finish

test/batch-test.go

@@ -1,37 +1,35 @@
-
 package main
 
 import (
-	"github.com/hpcng/warewulf/internal/pkg/batch"
 	"fmt"
-	"time"
 	"runtime"
+	"time"
+
+	"github.com/hpcng/warewulf/internal/pkg/batch"
 )
 
 func exampleJob(name string, id int) string {
 	fmt.Printf("[%d] %s started...\n", id, name)
-	time.Sleep(time.Second * 5)
+	time.Sleep(time.Second * time.Duration(id))
 	fmt.Printf("[%d] %s ending...\n", id, name)
 	return name
 }
 
-
 func main() {
 
 	fmt.Printf("GOMAXPROCS=%d\n", runtime.GOMAXPROCS(0))
 
-	jobstorun := 1000
+	jobstorun := 100
 
 	// create batch pool to run 100 jobs at a time every 10 seconds
-	batchpool := batch.New(100, 10)
+	batchpool := batch.New(10)
 	retvalues := make(chan string, jobstorun)
 
 	// submit a bunch of jobs
-	for i:=0; i<jobstorun; i++ {
+	for i := 0; i < jobstorun; i++ {
 
 		name := fmt.Sprintf("job-%04d", i)
-		id := i;
-
+		id := i
 		batchpool.Submit(func() {
 			retvalues <- exampleJob(name, id)
 		})
@@ -43,9 +41,8 @@ func main() {
 
 	close(retvalues)
 
-	for s:= range retvalues {
+	for s := range retvalues {
 		fmt.Printf("Return value is %s\n", s)
 	}
 
 }
-