sync Once | Singletons

04-sync-package/05-sync-once/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+ "fmt"
+ "sync"
+)
+
+func main() {
+ var wg sync.WaitGroup
+ var once sync.Once
+
+ load := func() {
+ fmt.Println("Run only once initialization function")
+ }
+
+ wg.Add(10)
+ for i := 0; i < 10; i++ {
+ go func() {
+ defer wg.Done()
+
+ // modify so that load function gets called only once.
+ // load()
+ once.Do(load)
+ }()
+ }
+ wg.Wait()
+}

README.md

@@ -299,4 +299,9 @@ cond := sync.NewCond(&mu)
 - Signal wakes one Goroutine waiting on `c`.
 - Broadcast wakes all Goroutines waiting on `c`.
 
------------
+-----------
+
+## sync.Once:
+- `sync.Once` is used to run one time initialization functions.
+- `once.Do(funcValue)` method accepts the initialization function.
+- `sync.Once` ensures that only one call to `Do` ever calls the function that is passed in - even on different Goroutines.