vlib/v/checker/tests/go_append_option_to_threads_err.vv:5:15: error: cannot append `thread !` to `[]thread`
    3 | fn main() {
    4 |     mut ths := []thread{}
    5 |     ths << spawn foo()
      |                  ~~~~~
    6 |     ths.wait()
    7 | }