start firefox with an extension and point it to a xvfb display

gowd.go

package main

import (
	"github.com/wirepair/webdriver"
	"log"
	"time"
)

func main() {
	desiredCapabilities := webdriver.Capabilities{"Platform": "Linux"}
	driver := webdriver.NewFirefoxDriver("firefox", "/tmp/webdriver.xpi")
	driver.Prefs["xpinstall.signatures.required"] = false // if firefox 42, must be development build
	driver.SetEnvironment("DISPLAY", ":1") // set display
	driver.AddExtension("/tmp/reddit-panel.xpi") // load an extension on start
	err := driver.Start()
	if err != nil {
		log.Fatalln(err)
	}
	session, _ := driver.NewSession(desiredCapabilities, desiredCapabilities)
	err = session.Url("http://golang.org")
	if err != nil {
		log.Println(err)
	}
	time.Sleep(30 * time.Second)
	session.Delete()
	driver.Stop()
}