GO by example, part 4

5-go-by-example/36-wait-group.go

@@ -0,0 +1,37 @@
+// wait for multiple goroutines to finish
+
+package main
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+// function to run in every goroutine
+func worker(id int) {
+	fmt.Printf("Worker %d starting\n", id)
+
+	time.Sleep(time.Second)
+	fmt.Printf("Worker %d done\n", id)
+}
+
+func main() {
+	// WaitGroup is used to wait for all the goroutines launched here to finish
+	var wg sync.WaitGroup
+
+	// Launch several goroutines and increment the WaitGroup counter for each
+	for i := 1; i <= 5; i++ {
+		wg.Add(1)
+		// Avoid re-use of the same i value in each goroutine closure
+		i := i
+		// Wrap the worker call in a closure that makes sure to tell the WaitGroup that this worker is done
+		go func() {
+			defer wg.Done()
+			worker(i)
+		}()
+	}
+	// Block until the WaitGroup counter goes back to 0
+	wg.Wait()
+
+}