error[E0277]: `UnsafeCell<[u8; 256]>` cannot be shared between threads safely
  --> src\test_class.rs:25:24
   |
25 | static CONTROL_BUFFER: UnsafeCell<[u8; 256]> = UnsafeCell::new([0; 256]);
   |                        ^^^^^^^^^^^^^^^^^^^^^ `UnsafeCell<[u8; 256]>` cannot be shared between threads safely
   |
   = help: the trait `Sync` is not implemented for `UnsafeCell<[u8; 256]>`
   = note: shared static variables must have a type that implements `Sync`