Remove internal/cmd/gen, it has no use for the end-developer.

Former-commit-id: 12bead9d379c6644e391c482fe71b2e88263376c

_examples/beginner/file-logger/main.go

@@ -43,7 +43,7 @@ func main() {
 	// navigate to http://localhost:8080
 	// and open the ./logs.txt file
 	if err := app.Run(iris.Addr(":8080"), iris.WithoutBanner); err != nil {
-		app.Log("Shutdown with error: %v", err)
+		app.Log("Shutdown with error: %v\n", err)
 
 	}
 }