GO by example, part 4

5-go-by-example/39-mutexes.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+// holds a map of counters
+// add a Mutex to synchronize access
+type Container struct {
+	mu       sync.Mutex
+	counters map[string]int
+}
+
+func (c *Container) inc(name string) {
+	// lock the mutex before accessing counters
+	c.mu.Lock()
+	// unlock it at the end of the function using defer
+	defer c.mu.Unlock()
+	c.counters[name]++
+}
+
+// mutex to safely access data across multiple goroutines
+func main() {
+	c := Container{
+		// the zero value of a mutex is usable as-is
+		counters: map[string]int{"a": 0, "b": 0},
+	}
+
+	var wg sync.WaitGroup
+
+	// increments a named counter in a loop
+	doIncrement := func(name string, n int) {
+		for i := 0; i < n; i++ {
+			c.inc(name)
+		}
+		wg.Done()
+	}
+
+	// run several goroutines concurrently
+	wg.Add(3)
+	go doIncrement("a", 10000)
+	go doIncrement("a", 10000)
+	go doIncrement("b", 10000)
+
+	// wait a for the goroutines to finish
+	wg.Wait()
+	fmt.Println(c.counters)
+}