finish a context pattern

README.md

@@ -48,6 +48,7 @@ Go常用的、面向工程化和最佳实践的模式套路，包含常见的23
 
 + [发布订阅模式(Pub-Sub)](./gomore/27_messages)
 + [时差模式(Time Profile)](./gomore/28_profiles)
++ [上下文模式(Context)](./gomore/29_context)
 
 ## 参考资料(Design patters Articles)
 

gomore/29_context/README.md

@@ -0,0 +1,3 @@
+# 上下文模式
+
+用于取消一个操作，可能是一个http请求，可能是一个Channel消息队列.

gomore/29_context/context_test.go

@@ -0,0 +1,54 @@
+package contexts
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"testing"
+	"time"
+)
+
+func TestContext(t *testing.T) {
+	go func() {
+		cContext()
+	}()
+
+	time.Sleep(time.Second)
+
+	reqest, err := http.NewRequest("GET", "http://localhost:8099/hello", nil) // http client get 请求
+	assertEq(nil, err)
+	client := &http.Client{}
+	ctx, cancel := context.WithCancel(context.Background())
+	reqest = reqest.WithContext(ctx)
+
+	go func() {
+		select {
+		case <-time.After(2 * time.Second):
+			cancel()
+		}
+	}()
+
+	response, err := client.Do(reqest)
+
+}
+
+func hello(w http.ResponseWriter, req *http.Request) {
+
+	ctx := req.Context()
+	defer fmt.Println("server: hello handler ended")
+
+	select {
+	case <-time.After(10 * time.Second):
+		fmt.Fprintf(w, "hello\n")
+	case <-ctx.Done():
+		err := ctx.Err()
+		fmt.Println("server:", err)
+		internalError := http.StatusInternalServerError
+		http.Error(w, err.Error(), internalError)
+	}
+}
+
+func cContext() {
+	http.HandleFunc("/hello", hello)
+	http.ListenAndServe(":8099", nil)
+}