c++ Linux input from console (inside docker container)

I'm trying to do something which seems very basic, to get user input with c++ in a linux console. However just using:

#include <iostream>

int main() 
{
    int amount;
    
    std::cout << "Input your number: ";
    std::cin >> amount;
}

It just skips the cin, i tried flushing the stream, but it doesnt matter. I have been looking for an answer for 2 days. But other people seem to be able to do it this way just fine.

The difference might be that I run it inside a docker container?