code: func (fds *FDSet) Set(fd uintptr) {
  	var i uint
  	for i = 0; i < fds.fd_count; i++ {
  		if fds.fd_array[i] == fd {
  			break
  		}
  	}
  	if i == fds.fd_count {
  		if fds.fd_count < FD_SETSIZE {
  			fds.fd_array[i] = fd
  			fds.fd_count++
  		}
  	}
  }
docs: // Set adds the fd to the set