The uploaded PDF is empty

[simaybocu]

I am uploading pdf with this library, the pdf is uploading successfully but it is empty. Can you help me what can I do please?

Code:

package main

import (
    "fmt"
    "io"
    "log"
    "net/http"
    "os"

    "github.com/gorilla/mux"
)

func UploadFile(w http.ResponseWriter, r *http.Request) {
    file, handler, err := r.FormFile("file")
    fileName := r.FormValue("file_name")
    if err != nil {
        panic(err)
    }
    defer file.Close()

    f, err := os.OpenFile(handler.Filename, os.O_WRONLY|os.O_CREATE, 0666)
    if err != nil {
        panic(err)
    }
    defer f.Close()
    _, _ = io.WriteString(w, "File "+fileName+" Uploaded successfully")
    _, _ = io.Copy(f, file)
}

func main() {
    router := mux.NewRouter().StrictSlash(true)
    router.HandleFunc("/file", UploadFile).Methods("POST")
    log.Fatal(http.ListenAndServe(":8081", router))
}

[andrewpillar]

When doing the io.Copy you're ignoring the error. Perhaps there is an error occuring when you try writing the file that is being missed. Could this be the cause for the file being empty at upload time?