求大神帮忙多线程问题，我想如果对字符变量进行修改进程就结束，但是这段代码输出修改的字符然后一直输出字符a这时什么原因.？

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;
#include <windows.h>
 
DWORD WINAPI Fun1Proc(LPVOID lpParameter);
  
char tickets='a';


void main()
{
    HANDLE hThread1 = NULL;
   
    hThread1=CreateThread(NULL,0,Fun1Proc,NULL,0,NULL);

    tickets = getchar();
   
    CloseHandle(hThread1);
   
    Sleep(4000);
      
}

DWORD WINAPI Fun1Proc(LPVOID lpParameter)
{
    while (true)
    {
     
        if (tickets == 'a')
        {
            Sleep(1000);
            cout<<tickets<<endl;
        }
        else
        {
           break;
        }
    }
      
    return 0;
}