使用gin，gin-contrib/sessions不同request path獲取不到session

gin session problem

從開發環境中抽出來了 sample code，https://github.com/dockerq/gin-session-problem，歡迎下載測試、重現問題。

環境

1. gin 版本 { "checksumSHA1": "86tapazS8gfJ5JRCxVNTTDkUZwM=", "path": "github.com/gin-gonic/gin", "revision": "bbd4dfee5056087c640a75c6cc21567f4f47585d", "revisionTime": "2017-07-12T07:01:46Z" }
2. golang 1.8.0

3. gin 中設定 session 程式碼

   r := gin.Default()
   
   store := sessions.NewCookieStore([]byte("secret"))
   store.Options(sessions.Options{
       MaxAge: int(30 * time.Minute), //30min
       Path:   "/",
   })
   
   r.Use(sessions.Sessions("mysession", store))
   r.GET("/pre", preSession)
   r.GET("/do", DoSomethine)
   r.Run(":8081")
   fmt.Println("start api server success.")
   

4. preSession(這個函式目的是向啟動的 gin.Engine 中新增一條 session 記錄)

   func preSession(c *gin.Context) {
   session := sessions.Default(c)
   session.Set("test@mail.com", "test.access.token")
   session.Save()
   c.JSON(http.StatusOK, nil)
   }
   

5. DoSomethine 函式接受 email 引數，讀取 session 中對應 email 的 value

   func DoSomethine(c *gin.Context) {
   userEmail := c.Query("user_email")
   if userEmail == "" {
       panic("can not get user email")
   }
   session := sessions.Default(c)
   userAccessToken := session.Get(userEmail)
   fmt.Printf("[DoSomethine] user access token is %s\n", userAccessToken)
   c.JSON(http.StatusOK, nil)
   }
   

6. 測試方法，先呼叫 getPreSession() 設定一條 session，然後訪問/do檢視是否拿到 session。

   func TestSession(t *testing.T) {
   StartTestServer(t)
   getPreSession()
   
   u := url.Values{}
   u.Set("user_email", "test@mail.com")
   testUrl := apiBaseUrl + "/do?" + u.Encode()
   fmt.Printf("test url is %s\n", testUrl)
   
   resp, err := http.Get(testUrl)
   defer resp.Body.Close()
   
   if err != nil {
       t.Error(err)
   }
   
   fmt.Println(resp.StatusCode)
   }
   

7. 結果，注意[DoSomethine] user access token is %! s(<nil>)表明沒有拿到 session。

   ➜  session make test 
   go test --cover -test.v
   === RUN   TestSession
   cookie of pre session request is [mysession=MTUwMTgxNDYxNnxEdi1CQkFFQ180SUFBUkFCRUFBQU9QLUNBQUVHYzNSeWFXNW5EQThBRFhSbGMzUkFiV0ZwYkM1amIyMEdjM1J5YVc1bkRCTUFFWFJsYzNRdVlXTmpaWE56TG5SdmEyVnV8cc0AwUddF90uWUxOF8BONUo-tFGouRdSOfj62m9U8sE=; Path=/; Expires=Wed, 09 Jan 1771 04:16:32 GMT; Max-Age=1800000000000]
   test url is http://0.0.0.0:8081/do?user_email=test%40mail.com
   [DoSomethine] user access token is %!s(<nil>)
   [GIN] 2017/08/04 - 10:43:36 | 200 |      99.642µs |       127.0.0.1 |  GET     /do
   200
   --- PASS: TestSession (2.00s)
       main_test.go:36: waiting 2 second for server startup
   PASS
   coverage: 48.0% of statements
   ok      ginlab/session  2.010s
   

問題

為什麼/pre設定 session 後，請求/do卻拿不到 session？是沒 session 沒有配置正確還是其它原因？