feat: add singleton

factory/README.md

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+《大话设计模式》-程杰-2007-1.10 简单工厂模式

singleton/README.md

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+https://lailin.xyz/post/singleton.html

singleton/hunger.go

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+package singleton
+
+type Singleton struct{}
+
+var singleton *Singleton
+
+func init() {
+	singleton = &Singleton{}
+}
+
+// GetHungerInstance
+//
+//	@Description: 饿汉式获取实例
+//	@return *Singleton
+func GetHungerInstance() *Singleton {
+	return singleton
+}

singleton/hunger_test.go

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+package singleton
+
+import (
+	"testing"
+)
+
+func TestHunger(t *testing.T) {
+	s1 := GetHungerInstance()
+	s2 := GetHungerInstance()
+	if s1 == s2 {
+		t.Log("success")
+	} else {
+		t.Fatal("failure")
+	}
+}
+
+func BenchmarkHunger(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if GetHungerInstance() != GetHungerInstance() {
+				b.Errorf("test fail")
+			}
+		}
+	})
+}

singleton/lazy.go

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+package singleton
+
+import "sync"
+
+var (
+	lazySingleton *Singleton
+	once          = &sync.Once{}
+)
+
+// GetLazyInstance
+//
+//	@Description: 懒汉式
+//	@return *Singleton
+func GetLazyInstance() *Singleton {
+	if lazySingleton == nil {
+		once.Do(func() {
+			lazySingleton = &Singleton{}
+		})
+	}
+	return lazySingleton
+}

singleton/lazy_test.go

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+package singleton
+
+import "testing"
+
+func TestGetLazyInstance(t *testing.T) {
+	if GetLazyInstance() != GetLazyInstance() {
+		t.Fatal("lazy instance failed")
+	} else {
+		t.Log("lazy instance succeeded")
+	}
+}
+
+func BenchmarkGetLazyInstance(b *testing.B) {
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if GetLazyInstance() != GetLazyInstance() {
+				b.Errorf("test fail")
+			}
+		}
+	})
+}