code: func (c *connectionFlowController) EnsureMinimumWindowSize(inc protocol.ByteCount) {
  	c.mutex.Lock()
  	if inc > c.receiveWindowSize {
  		c.logger.Debugf("Increasing receive flow control window for the connection to %d kB, in response to stream flow control window increase", c.receiveWindowSize/(1<<10))
  		c.receiveWindowSize = utils.MinByteCount(inc, c.maxReceiveWindowSize)
  		c.startNewAutoTuningEpoch()
  	}
  	c.mutex.Unlock()
  }
docs: // EnsureMinimumWindowSize sets a minimum window size
  // it should make sure that the connection-level window is increased when a stream-level window grows