Safari无法发送Cookie-HTTP：不存在命名的Cookie

My backend is Golang. I use the following code to to set an http cookie to the browser, like so:

cookie := http.Cookie{Name: "user", Value: strCookie, MaxAge: 86400, Secure: true, HttpOnly: true}
http.SetCookie(w, &cookie)

In the next http session, I use the following code to try to read the cookie:

cookieUser, err := r.Cookie("user")

It works with Chrome, Firefox, but Safari failed to send the cookie back to the backend, therefore the Golang tried to read the cookie, it shows the error message:

http: named cookie not present

So I'm wondering whether this is a Safari specific bug or there's any problem in my program.