Is embedding a directory supported for cross-compilation? - go

Question

Summary of the problem: access to embedded files in directories work for a native compilation but not for cross-compiled code
I have the following code that embeds a file (static/index.html) in a directory and exposes it via HTTP:
package main
import (
"embed"
"net/http"
"os"
"github.com/gorilla/handlers"
"github.com/gorilla/mux"
"github.com/rs/cors"
"github.com/rs/zerolog/log"
)
//go:embed static
var content embed.FS
func main() {
// API and static site
r := mux.NewRouter()
r.Use(mux.CORSMethodMiddleware(r))
r.Use(func(next http.Handler) http.Handler {
return handlers.LoggingHandler(os.Stdout, next)
})
c := cors.New(cors.Options{
AllowCredentials: true,
//Debug: true,
})
handler := c.Handler(r)
r.PathPrefix("/").Handler(http.FileServer(http.Dir("./static/")))
log.Info().Msg("starting dash webserver at port 1495")
_ = http.ListenAndServe("0.0.0.0:1495", handler)
}
I compiled this code (go1.16.7) in Windows 10 WSL2 (EDIT: and in native Windows 10) via go build -o goembed.wsl2. When started, running curl localhost:1495 gives the right result (the text in index.html).
I then compiled it (still in WSL2/Win10) via env GOOS=linux GOARCH=amd64 go build -o goembed.linux (or the relevant incantation in Windows 10 to set the environment variables) and started goembed.linux on an Ubuntu 18.04 server.
The program started but the output of curl localhost:1495 was 404 File Not Found.
Why is it so?
Interestingly, embedding a single file (the variable containing it is then of type []byte) exposes it correctly via the HTTP server in both binaries (the native WSL one, and the amd64).
EDIT: I have the same behaviour when compiling in native Windows 10, I updated the references above

Answer 1

It is a mistake from my side: I embed static but serve ./static/ which is the local (OS) directory, instead of the embedded one. It should be:
r.PathPrefix("/").Handler(http.FileServer(http.FS(content)))