Press enter to continue (in switch)

I searched on the internet for several times to find a way to do "Press enter to continue".
But some of them were only suitable on Windows (ex. system("Pause" ), )  and others were too complex. So I decided to use "Press enter to continue", which is more easy, instead, for my program.



The way I chosen was using cin.ignore(). In c++ reference, the function is described:

Extracts characters from the input sequence and discards them.
The extraction ends when n characters have been extracted and discarded or when the character delim is found, whichever comes first. In the latter case, the delim character itself is also extracted.

I wrote a subroutine as below:

void PETC() {   //press enter to continue
     cout << "Press ENTER to continue...\n";          

     cin.ignore(std::numeric_limits<streamsize>::max(),'\n');
}

It worked fine until I put the subroutine in switch conditional judgement, which looks like:

char cmd;
.
.
.
cin >> cmd;
switch (cmd) {
      case '1':
          .
          .
          PETC();
          break;
   
       case '2':
          .
          .
          PETC();
          break;
} 

PETC() dose not work! It shows "Press ENTER to continue...", but it does not wait for me to press enter. I put it away for two days because it was Chinese New Year :p. Two days latter, I opened my code and worked it for a morning. I thought it might because the  cin before switch (and otherwhere) leaves return in input buffer. My solution was modifying the PETC() as:

void PETC() {   //press enter to continue
     cout << "Press ENTER to continue...\n";          

     cin.ignore(std::numeric_limits<streamsize>::max(),'\n');

     cin.ignore(std::numeric_limits<streamsize>::max(),'\n');
}

And it worked!