output-transparent-pixel.go

import (
    "fmt"
    "net/http"
    "time"
)

const transPixel = "\x47\x49\x46\x38\x39\x61\x01\x00\x01\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x21\xF9\x04\x01\x00\x00\x00\x00\x2C\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x02\x44\x01\x00\x3B"

func pixelHandler(w http.ResponseWriter, r *http.Request) {
      // Pixel
      w.Header().Set("Content-Type", "image/gif")
      w.Header().Set("Last-Modified", time.Now().UTC().Format(http.TimeFormat))
      w.Header().Set("Expires", "Wed, 11 Nov 1998 11:11:11 GMT")
      w.Header().Set("Cache-Control", "no-store, no-cache, must-revalidate, post-check=0, pre-check=0")
      w.Header().Set("Pragma", "no-cache")
      fmt.Fprintf(w, transPixel)
}