Bagaimanakah Saya Boleh Menghantar Data daripada Middleware kepada Pengendali di Golang?

import (
    "github.com/gorilla/context"
)

func Middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Middleware operations
        // Parse body/get token.
        context.Set(r, "token", token)

        next.ServeHTTP(w, r)
    })
}

func Handler() http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token := context.Get(r, "token")
    })
}

token := context.Get(r, "token")

func Middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Middleware operations
        // Parse body/get token.
        ctx := context.WithValue(r.Context(), "token", token)

        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

func Handler() http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token := r.Context().Value("token")
    })
}