From d382010cbcf634cc6a4724895b182c6d3b837607 Mon Sep 17 00:00:00 2001
From: Hoshea <fgksgf@gmail.com>
Date: Sat, 1 May 2021 16:40:11 +0800
Subject: [PATCH] update singleton

---
 03_singleton/singleton.go      | 24 +++++++++++++++++-------
 03_singleton/singleton_test.go |  3 +--
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/03_singleton/singleton.go b/03_singleton/singleton.go
index c99a380..9f269ab 100644
--- a/03_singleton/singleton.go
+++ b/03_singleton/singleton.go
@@ -2,17 +2,27 @@ package singleton
 
 import "sync"
 
-//Singleton 是单例模式类
-type Singleton struct{}
+// Singleton 是单例模式接口，导出的
+// 通过该接口可以避免 GetInstance 返回一个包私有类型的指针
+type Singleton interface {
+	foo()
+}
+
+// singleton 是单例模式类，包私有的
+type singleton struct{}
+
+func (s singleton) foo() {}
 
-var singleton *Singleton
-var once sync.Once
+var (
+	instance *singleton
+	once     sync.Once
+)
 
 //GetInstance 用于获取单例模式对象
-func GetInstance() *Singleton {
+func GetInstance() Singleton {
 	once.Do(func() {
-		singleton = &Singleton{}
+		instance = &singleton{}
 	})
 
-	return singleton
+	return instance
 }
diff --git a/03_singleton/singleton_test.go b/03_singleton/singleton_test.go
index f143b33..edf9908 100644
--- a/03_singleton/singleton_test.go
+++ b/03_singleton/singleton_test.go
@@ -19,7 +19,7 @@ func TestParallelSingleton(t *testing.T) {
 	start := make(chan struct{})
 	wg := sync.WaitGroup{}
 	wg.Add(parCount)
-	instances := [parCount]*Singleton{}
+	instances := [parCount]Singleton{}
 	for i := 0; i < parCount; i++ {
 		go func(index int) {
 			//协程阻塞，等待channel被关闭才能继续运行
@@ -37,4 +37,3 @@ func TestParallelSingleton(t *testing.T) {
 		}
 	}
 }
-