Go application to upload files, delete existing files, and update existing files.

Features:

Uploads files with size validation and type checking (supports jpeg, jpg, png, gif, and pdf).
Generates random filenames to avoid conflicts.
Stores uploaded files in a temporary directory.
Provides endpoints for:
    Uploading files (/upload) - Accepts a multipart form data with a file named "uploadFile".
    Deleting files (/delete) - Requires a POST request with a form value named "fileName".
    Updating files (/update) - Requires a POST request with a form value named "uploadFile" and "fileName" (for the existing file to update).
Serves uploaded files through a static file server (/files/).

Running the Application:

Save the code as main.go.
Run the application using go run main.go.
Access the upload interface at http://localhost:8080/upload.

Using the Uploader:

http://localhost:8080/upload in your browser.
Select a file to upload.
Click "Upload File".
Upon successful upload, you'll receive a message with a link to access the uploaded file (/files/<filename>).

File Deletion:

The frontend functionality for deletion is not yet implemented (requires JavaScript integration). However, you can manually delete files using the /delete endpoint.
Send a POST request to http://localhost:8080/delete with a form value named "fileName" set to the filename of the file you want to delete.

File Update:

Similar to deletion, the frontend functionality for updating files is not yet implemented.
Send a POST request to http://localhost:8080/update with two form values:
    "uploadFile": The new file content to update the existing file with.
    "fileName": The filename of the existing file to update.