HTTP File Upload and Download Implementation

This Go HTTP server handles file uploads and serves files for download:

package main

import (
  "crypto/rand"
  "fmt"
  "io"
  "net/http"
  "os"
  "path/filepath"
)

const (
  uploadDir = "storage"
  maxSize   = 10 << 20 // 10MB
)

func main() {
  http.HandleFunc("/upload", uploadHandler)
  http.Handle("/static/", http.StripPrefix("/static/", 
      http.FileServer(http.Dir(uploadDir))))
  
  http.ListenAndServe(":8888", nil)
}

func uploadHandler(w http.ResponseWriter, r *http.Request) {
  r.ParseMultipartForm(maxSize)
  
  file, header, err := r.FormFile("file")
  if err != nil {
    http.Error(w, "Invalid file", http.StatusBadRequest)
    return
  }
  defer file.Close()

  if header.Size > maxSize {
    http.Error(w, "File too large", http.StatusRequestEntityTooLarge)
    return
  }

  fileBytes, err := io.ReadAll(file)
  if err != nil {
    http.Error(w, "Read error", http.StatusInternalServerError)
    return
  }

  uniqueName := generateID(12) + filepath.Ext(header.Filename)
  filePath := filepath.Join(uploadDir, uniqueName)
  
  if err := os.WriteFile(filePath, fileBytes, 0666); err != nil {
    http.Error(w, "Save failed", http.StatusInternalServerError)
    return
  }
  
  w.Write([]byte("Upload successful"))
}

func generateID(length int) string {
  b := make([]byte, length)
  rand.Read(b)
  return fmt.Sprintf("%x", b)
}

Cross-Platform Browser Launching

This implementation opens URLs in the default browser across different operating systems:

package main

import (
  "os/exec"
  "runtime"
)

func main() {
  openBrowser("http://localhost:8889")
}

func openBrowser(url string) error {
  var cmd string
  var args []string

  switch runtime.GOOS {
  case "windows":
    cmd = "cmd"
    args = []string{"/c", "start", url}
  case "darwin":
    cmd = "open"
    args = []string{url}
  default: // Linux and BSD
    cmd = "xdg-open"
    args = []string{url}
  }
  
  return exec.Command(cmd, args...).Start()
}