How to use esc to stop a program in the middle of its execution in C?

Using the getch function, you can get the character that was typed in the console, in which case the number 27 represents the keyboard ESC.

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

int main()
{
    char opcao;
    while(opcao != 27)
    {
        printf("\n\n\nEscolha uma opcao:\n");

        printf("<esc> para sair\n\n");

        opcao = getch();

        if (opcao != 27)
        {
            printf("Voce nao apertou ESC\n\n");
        }     
    }       
    return 0;
}