如何通过功能传递应用程序？

Question

In main, the app is started as such:

// ...

func main () {
    initializeAppDefault()
    go lib.GetData()
    http.HandleFunc("/_ah/somepoint", lib.SomeHandler)
// .. 

func initializeAppDefault() *firebase.App {
    // [START initialize_app_default]
    app, err := firebase.NewApp(context.Background(), nil)
    if err != nil {
        log.Fatalf("error initializing app: %v
", err)
    }
    // [END initialize_app_default]
    return app
}

In SomeHandler, I need the app which initializeAppDefault returns, to verify a JSON Web Token(JWT).

func SomeHandler(w http.ResponseWriter, r *http.Request) {
    // Set content type:
    w.Header().Set("Content-Type", "application/json")

    if r.Header != nil {
        ReqToken := r.Header.Get("Authorization")
        splitToken := strings.Split(ReqToken, "Bearer")
        ReqToken = splitToken[1]
        fmt.Println(ReqToken)
        // Verify JWT
        // If it's invalid, return?

        verifyIDToken(app, ReqToken)
        // How do I pass the app in here?

func verifyIDToken(app *firebase.App, idToken string) *auth.Token {
// ... 

My question is, when the app is initialized in the main.go file by invoking initializeAppDefault(), how do I pass it to the SomeHandler which handles requests at /_ah/somepoint?

Answer 1

The way to pass arbitrary dependencies into an HTTP handler function is by returning a closure:

func myHandler(a *Something, b *SomethingElse) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // The body of the handler here, using a and b
    }
}

Then you'll use it as:

http.Handle("/some/path", myHandler(a, b))