add more details

cmd/root.go

@@ -17,6 +17,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package cmd
 
 import (
+	"log"
 	"os"
 
 	"github.com/spf13/cobra"
@@ -46,7 +47,16 @@ func handleEvent(event sdl.Event, m *milkDropWindow) bool {
 }
 
 func milkbucket(cmd *cobra.Command, args []string) {
-	err := sdl.Init(sdl.INIT_VIDEO)
+	fi, err := os.Stdin.Stat()
+	if err != nil {
+		panic(err)
+	}
+	size := fi.Size()
+	if size <= 0 {
+		log.Fatal("stdin is empty")
+	}
+
+	err = sdl.Init(sdl.INIT_VIDEO)
 	if err != nil {
 		panic(err)
 	}