how to enable gqlgen server for CORS issue? - go

Question

GOAL:
Svelte app running on port 5000 wants to query data from gqlgen GraphQL server running on port 8080, both on localhost. I tried to query a public graphql API such as https://api.react-finland.fi/graphql just to test if my Svelte app (port:5000) is working well and it is. So I think the problem lies with my Go graphql server (port:8080).
SYSTEM
go version
go version go1.15 linux/amd64
go 1.15
require (
github.com/99designs/gqlgen v0.12.1
github.com/go-chi/chi v4.1.2+incompatible
github.com/gorilla/websocket v1.4.2
github.com/rs/cors v1.7.0
github.com/vektah/gqlparser/v2 v2.0.1
)
HAVE TRIED
According to the official site, I have tried their approach.
And here is my code:
func main() {
port := os.Getenv("PORT")
if port == "" {
port = defaultPort
}
router := chi.NewRouter()
// Add CORS middleware around every request
// See https://github.com/rs/cors for full option listing
router.Use(cors.New(cors.Options{
AllowedOrigins: []string{"http://localhost:5000", "http://localhost:8080"},
AllowOriginFunc: func(origin string) bool { return true },
AllowedMethods: []string{},
AllowedHeaders: []string{},
AllowCredentials: true,
Debug: true,
}).Handler)
srv := handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))
srv.AddTransport(&transport.Websocket{
Upgrader: websocket.Upgrader{
CheckOrigin: func(r *http.Request) bool {
// Check against your desired domains here
return r.Host == "localhost:8080"
},
ReadBufferSize: 1024,
WriteBufferSize: 1024,
},
})
http.Handle("/", playground.Handler("GraphQL playground", "/query"))
http.Handle("/query", srv)
log.Printf("connect to http://localhost:%s/ for GraphQL playground", port)
log.Fatal(http.ListenAndServe(":"+port, nil))
err := http.ListenAndServe(":8080", router)
if err != nil {
panic(err)
}
}
RESULT
I got those errors:
Access to fetch at 'http://localhost:8080/' from origin 'http://localhost:5000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
HOW TO SOLVE?
I've read quite some documentation and googled around... but couldn't figure out exactly how to and I don't know how to debug to find solution. I just learnt GO for two days so far. Can someone help? Thanks!

Answer 1

Hi now someone helped me find out the major problems I have:
1.Yes, we can use just one in the line where I wrote :
AllowedOrigins: []string{"http://localhost:5000", "http://localhost:8080"},
AllowOriginFunc: func(origin string) bool { return true },
In fact the second one will overwrite the first one, so can choose just one.
2.In this part
log.Fatal(http.ListenAndServe(":"+port, nil))
err := http.ListenAndServe(":8080", router)
if err != nil {
panic(err)
}
I have written the http:ListenAndServe twice, so it didn't get to the second one. I deleted the log.Fatal(http.ListenAndServe(":"+port, nil))
3.Since we passed the middleware to router for http request, we need to use that instead of http.handle. So those two lines were wrong:
http.Handle("/", playground.Handler("GraphQL playground", "/query"))
http.Handle("/query", srv)
The right way to do it should be :
router.Handle("/", playground.Handler("GraphQL playground", "/query"))
router.Handle("/query", srv)
In fact that was shown in the official approach... but somehow after I tried several different solutions I got lost in the rabbit holes and didn't see those obvious errors! >.<
After the above changes now it works finally! Thanks for your help!