dokerimg: clean up temp dir
diff --git a/dockerimg/dockerimg.go b/dockerimg/dockerimg.go
index 8ebb13d..0e612aa 100644
--- a/dockerimg/dockerimg.go
+++ b/dockerimg/dockerimg.go
@@ -365,6 +365,7 @@
 	if err != nil {
 		return "", err
 	}
+	defer os.RemoveAll(tmpGopath)
 
 	start := time.Now()
 	cmd := exec.CommandContext(ctx, "go", "install", "sketch.dev/cmd/sketch@latest")