In this blog, we will learn about Golang Multipart File Upload using Form File.
Uploading Files on the server is useful in many scenarios like uploading your resume on a job portal, uploading your picture on any website or social media.
HTML Template for Uploading File
In this example, we are using bootstrap starter code for the design of the template.
Learn how to parse templates in Golang.
<form action="/upload" method="POST" class="form-group" enctype="multipart/form-data">
<label for="file">File :</label>
<input type="file" name="file" id="file">
<input type="submit" value="Upload File" name="submit" class="btn btn-success">
</form>Upload File in Golang
Create fileupload.go file, we will define all the handlers and routes in this Go file.
Parsing HTML Templates
First of all the HTML template for file uploading will be parsed and will be executed for the "/" route.
var parsedTemplate *template.Template
func init() {
parsedTemplate, _ = template.ParseFiles("template/index.html")
}
func index(w http.ResponseWriter, r *http.Request) {
parsedTemplate.Execute(w, nil)
}Multipart File Upload Function
func fileUploadHandler(w http.ResponseWriter, r *http.Request) {
r.ParseMultipartForm(10 << 20)
file, header, err := r.FormFile("file")
if err != nil {
log.Println("Error Getting File", err)
return
}
defer file.Close()
out, pathError := ioutil.TempFile("temp-images", "upload-*.png")
if pathError != nil {
log.Println("Error Creating a file for writing", pathError)
return
}
defer out.Close()
_, copyError := io.Copy(out, file)
if copyError != nil {
log.Println("Error copying", copyError)
}
fmt.Fprintln(w, "File Uploaded Successfully! ")
fmt.Fprintln(w, "Name of the File: ", header.Filename)
fmt.Fprintln(w, "Size of the File: ", header.Size)
}
First of all, we set the limit for the size of the file to be uploaded on the server using the ParseMultipartForm function from the request parameter.
Then FormFile handler is called on the HTTP request to get the file that is uploaded. The defer statement closes the file once the function returns.
when the uploaded file is received we need to store it somewhere so a temporary folder is created, the file name is preceded by “upload-” and the extension for the file is “.png”. If there occurs any kind of error while folder creation the error is logged out and the function returns without going further.
After that, we copy the uploaded file to the path created.
When all this process is completed and no error occurs, we print a success message along with the details of the file to the web page.
Learn more about Golang Multipart File Upload using Form File from Golang.org.