While loop stops Timer from running (Dart)

I have a question about while loop in dart.

This is a piece of code:

bool temp = false;
Timer(Duration(milliseconds: 5), () {
    print('In timer:' + temp.toString());
    temp = true;
});
Timer(Duration(milliseconds: 1000), () {
    print('In timer:' + temp.toString());
});

The result is exactly what I expect:

false (after 5 ms)
true (after 1 s)

But when add while loop:

bool temp = false;
Timer(Duration(milliseconds: 5), () {
    print('In timer:' + temp.toString());
    temp = true;
});

while (!temp) {}
print('End');

I expect that it will print out the console like this:

false
End (immediately after false)

But everything stucks in while loop and the timer doesn't seem to run to update temp anymore. May I get any explanation?