From 1576d64ec1bdd311e8ad7e1132217c02d708b38e Mon Sep 17 00:00:00 2001
From: lifeilin01 <lifeilin01@58.com>
Date: Sun, 23 May 2021 19:08:50 +0800
Subject: [PATCH] =?UTF-8?q?feat:=E5=A2=9E=E5=8A=A0=E9=A2=98=E7=9B=AE?=
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---
 README.md        |  1 +
 question/q022.md | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 question/q022.md

diff --git a/README.md b/README.md
index c47fc1b..8aa552b 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,7 @@
 - [简单聊聊内存逃逸？](question/q019.md)
 - [字符串转成byte数组，会发生内存拷贝吗？](question/q020.md)
 - [http包的内存泄漏](question/q021.md)
+- [sync.Map 的用法](question/q022.md)
 
 ## Golang 理论
 
diff --git a/question/q022.md b/question/q022.md
new file mode 100644
index 0000000..6e34ac7
--- /dev/null
+++ b/question/q022.md
@@ -0,0 +1,34 @@
+# sync.Map 的用法
+
+## 问题
+
+```go
+package main
+
+import (
+	"fmt"
+	"sync"
+)
+
+func main(){
+	var m sync.Map
+	m.Store("address",map[string]string{"province":"江苏","city":"南京"})
+        v,_ := m.Load("address")
+	fmt.Println(v["province"]) 
+}
+```
+
+- A，江苏；
+- B`，v["province"]`取值错误；
+- C，`m.Store`存储错误；
+- D，不知道
+
+## 解析
+
+`invalid operation: v["province"] (type interface {} does not support indexing)`
+因为 `func (m *Map) Store(key interface{}, value interface{})`
+所以 `v`类型是 `interface {}` ，这里需要一个类型断言
+
+```go
+fmt.Println(v.(map[string]string)["province"]) //江苏
+```