Is it possible to make a curved gradient in Adobe Illustrator?

Question

Adobe Illustrator

It is necessary to make the wriggling gradient change color not in a straight line, but taking into account all the bends of the contour (or maybe even shapes).
This is how it usually happens:

And this is how you can do it yourself using three different layers:

How to do the same thing without using three layers. In order not to set up three different gradients and not bathe with manipulators? Trite on the example of the letter S or C.

Answer 1

All this is in the gradient settings:
www.youtube.com/watch?v=oreSgfkVm5I