docs: def bg(func):
      """Run a function in background, will not block main thread's exit.(thread.daemon=True)
      ::
  
          from torequests.utils import bg, print_info
          import time
  
          def test1(n):
              time.sleep(n)
              print_info(n, 'done')
  
          @bg
          def test2(n):
              time.sleep(n)
              print_info(n, 'done')
  
          test3 = bg(test1)
  
          test2(1)
          test3(1)
          print_info('not be blocked')
          time.sleep(2)
  
          # [2018-06-12 23:46:19](L81): not be blocked
          # [2018-06-12 23:46:20](L81): 1 done
          # [2018-06-12 23:46:20](L81): 1 done
      """
  
      @wraps(func)
      def wrapper(*args, **kwargs):
          t = Thread(target=func, args=args, kwargs=kwargs)
          t.daemon = True
          t.start()
          return t
  
      return wrapper