Flex span auto width if line wraps?

Question

css

If the span in flex wraps to the second line, the width becomes 100%, how do I set the width to auto?
Example :

<div>
  <span>1234567890 1234</span>
</div>

div{
  width: 100px;
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: red;
}
span{
  background: green;
}

Result:

And you need the span to be not the full width, but the size of the text and the text itself was on the left side, like this:

But without setting the width of the span in advance

Answer 1

Like this https://jsfiddle.net/wx6mg2mj/
But it's not clear why flex

Answer 2

Wrap span with another div like
Example