fixed dependency on image/png

window/glfw.go

@@ -11,6 +11,7 @@ import (
 	"github.com/go-gl/glfw/v3.2/glfw"
 	"os"
 	"image"
+	_ "image/png"
 	"bytes"
 	"github.com/g3n/engine/gui/assets"
 )