Practice singleton

Signed-off-by: Bruce <weichou1229@gmail.com>

playground/singleton/internal/singleton.go

@@ -0,0 +1,27 @@
+package internal
+
+import (
+	"fmt"
+	"sync"
+)
+
+// singleton is private struct, it should be created and fetched by GetSingletonObject func
+type singleton struct {
+}
+
+func (singleton) SayHi() {
+	fmt.Println("Hi!")
+}
+
+var (
+	once     sync.Once
+	instance singleton
+)
+
+func GetSingletonObject() singleton {
+	once.Do(func() {
+		instance = singleton{}
+	})
+
+	return instance
+}

playground/singleton/main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/weichou1229/go-patterns/playground/singleton/internal"
+)
+
+func main() {
+	var s = internal.GetSingletonObject()
+	s.SayHi()
+}