Exception "Global evaluation requires a thread to have been loaded" on VSCode when reading values with Dart

I've been trying to run a Dart code like that on VSCode:

import "dart:io";
void main() {
  print("Input a number");
  int numA = int.parse(stdin.readLineSync()!);
  print("The number is $numA");
}

However, after printing "Input a number" for the user input a number (duh), the program freezes with the message Global evaluation requires a thread to have been loaded:

The same program runs fine everywhere, e.g., JDoodle and IntelliJ. Any clue of what is happening, folks? No thread here on Stackoverflow provided an answer.