Go - Slices - 3

• Ex. Slice is in the middle of an array, what will happen in that array after append?
  => Array value will reflect slice change, but array instance will change after appended slice capacity larger than array
• Ex, Use built-in function copy to copy elements from one slice to another
  Copy won't work if length is not enough
  
• Copied slice refer to the same array? What will happen when we modify value from copied slice?
  => Modification in copied slice won't affect original array.
• Must not assume modification in old slice will affect new slice
  
• Ex. Declare function with ... makes function variadic, can accept any numbers of arguments.
  
• Ex. Remove the middle of a slice.
  It seems underlying array won't be removed when we just remove from slice, need to be careful of this part.
  Easy to confuse.