Guide to creating a multiple image upload form using Golang
A step-by-step guide on how to create a form to upload multiple images simultaneously in Golang using the `net/http` library.
In this article, we will learn how to create an HTML form to upload multiple images and then process these files using Golang. We will use the net/http library to handle receiving the form data and storing the images in a destination folder.
Golang code:
package main
import (
"fmt"
"io"
"net/http"
"os"
"path/filepath"
)
func uploadHandler(w http.ResponseWriter, r *http.Request) {
// Limit the size of the memory used for processing the upload
r.ParseMultipartForm(10 << 20)
// Retrieve the uploaded files from the form
files := r.MultipartForm.File["files"]
for _, fileHeader := range files {
// Open the uploaded file
file, err := fileHeader.Open()
if err != nil {
http.Error(w, "Unable to open file", http.StatusInternalServerError)
return
}
defer file.Close()
// Create a new file to store the uploaded content
dst, err := os.Create(filepath.Join("uploads", fileHeader.Filename))
if err != nil {
http.Error(w, "Unable to save file", http.StatusInternalServerError)
return
}
defer dst.Close()
// Copy the uploaded file content to the new file
if _, err := io.Copy(dst, file); err != nil {
http.Error(w, "Unable to copy file", http.StatusInternalServerError)
return
}
}
fmt.Fprintln(w, "Upload successful!")
}
func main() {
// Create the storage directory if it doesn't exist
os.MkdirAll("uploads", os.ModePerm)
// Define the handler for the /upload path
http.HandleFunc("/upload", uploadHandler)
// Create the HTML page for the upload form
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, `<html><body>
<form action="/upload" method="post" enctype="multipart/form-data">
Select multiple images: <input type="file" name="files" multiple>
<input type="submit" value="Upload">
</form>
</body></html>`)
})
fmt.Println("Server running at http://localhost:8080")
http.ListenAndServe(":8080", nil)
}
Detailed explanation:
-
r.ParseMultipartForm(10 << 20): Limits the memory used for processing the file upload to 10MB. -
files := r.MultipartForm.File["files"]: Retrieves the list of uploaded files from the form. -
os.Create(filepath.Join("uploads", fileHeader.Filename)): Creates a new file in the "uploads" directory to store the uploaded file. -
io.Copy(dst, file): Copies the uploaded file content to the new file on the server. -
http.HandleFunc("/upload", uploadHandler): Defines the path that handles image upload requests. -
http.ListenAndServe(":8080", nil): Starts the server on port 8080.
System Requirements:
- Go version 1.16 or higher
How to install Golang:
Download and install Golang from the official Go website.
Tips:
- Ensure that the "uploads" directory has write permissions to store uploaded files.
- Validate the file size and type before saving to avoid security vulnerabilities.