or-done.go

orDone := func(done, c <-chan interface{}) <-chan interface{} {
  valStream := make(chan interface{})
  go func() {
    defer close(valStream)
    for {
      select {
      case <-done:
        return
      case v, ok := <-c:
        if ok == false {
          return
        }
        select {
        case valStream <- v:
        case <-done:
        }
      }
    }
  }()
  return valStream
}