Very stretchy knit fabrics are not the easiest to hem with a regular sewing machine. Best options are using a twin needle or doing a blind hem by hand.
There's a quicker way that's especially useful with linings that are not showing. This hemming technique creates quite a visible stitch so if you are using it on a visible hem make sure to practise first.
Set your stitch to a narrow zig zag and your presser foot pressure to low. Use a special needle for knit fabrics. We're creating a rolled hem. Roll the hem towards the wrong side - many knits tend to curl up anyway so all you have to do is measure the width and make sure it stays constant. You can either pin the hem in place first or just roll and measure as you go along.
It's important to use a zig zag stitch, otherwise the thread will break as the fabric stretches. Try not to stretch the fabric as you're sewing, instead push it slightly towards the feed dogs to keep the fabric stiff.