If you need a hint, I'll be there for you

I’m always ahead, yet never in reach, A silent line where sky and earth meet. You chase me at dawn, I fade at night, A boundary drawn in shifting light. What am I?

An indoor space to encourage sled dogs to go faster, perhaps?

Why Johnny went the extra mile; he missed his . . . .

I can be made of many things: paper, metal, plastic, people. I am a decoration and a tool. I’m known for linking items together.