Even better, "GO uphill"! It may--or may not--require a turn, depending on the direction you are already going, and on the terrain ahead of you.
OR--learn how to use the brakes. There are TWO, and only two, ways to slow down. One is to increase the resistance--usually by scrubbing off speed with skidding skis, but also including falling down, dragging poles, running into deeper snow, hitting a tree.... The other is to go uphill. Speed control from FRICTION, or speed control from DIRECTION.
The first is defensive, using the skis as brakes. The second is offensive, using the skis to control direction. They both work, and of course, all expert skiing requires mastery of both ways. But good skiing habits involve controlling speed with line (direction) as a habit, and braking only when necessary. As I've often said, good skiing involves the habit of "skiing a slow enough line as fast as you can--when you can" (and braking when you have to)!
It is ironic but true that the faster we go, the more dangerous it becomes to hit the brakes! Braking is the first instinct for most skiers, especially beginners, and it can become a deeply-ingrained and frustrating habit.