How can I use multiple uvSet in GLSL shaders?

I’m pretty new to Maya, and I’m trying to write some data l to uvSet-2 , and In my GLSL shader, I will use this data to do some shading operation. I’ve tried to access the uvSet-2 by defining my VertexInput struct as following:

attribute APPDATA {
vec3 Position : POSITION;
vec2 UV : TEXCOORD0;
vec2 UV1 :TEXCOORD1;
vec2 UV2 :TEXCOORD2;
vec3 Normal : NORMAL;
vec4 Color : COLOR0;
But no matter how I changed the vertex uvs, it seems that I still got the same value in shader, I wonder if what i wrote is not the right way to use differetn uvSet?