GO by example, part 4

5-go-by-example/38-atomic-counters.go

@@ -0,0 +1,35 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+)
+
+// atomic counters accessed by multiple goroutines
+func main() {
+	// unsigned integer to represent our (always-positive) counter
+	var ops uint64
+
+	// WaitGroup will help wait for all goroutines to finish their work
+	var wg sync.WaitGroup
+
+	// start 50 goroutines that each increment the counter exactly 1000 times
+	for i := 0; i < 50; i++ {
+		wg.Add(1)
+
+		go func() {
+			for c := 0; c < 1000; c++ {
+				// atomically increment the counter, giving it the memory address of ops counter with the & syntax
+				atomic.AddUint64(&ops, 1)
+			}
+			wg.Done()
+		}()
+	}
+
+	// wait until all the goroutines are done
+	wg.Wait()
+
+	// it’s safe to access ops now because it's known no other goroutine is writing to it
+	fmt.Println("ops:", ops)
+}