code: func (c *channelPool) Release() {
  	c.mu.Lock()
  	conns := c.conns
  	c.conns = nil
  	c.factory = nil
  	c.ping = nil
  	closeFun := c.close
  	c.close = nil
  	c.mu.Unlock()
  
  	if conns == nil {
  		return
  	}
  
  	close(conns)
  	for wrapConn := range conns {
  		closeFun(wrapConn.conn)
  	}
  }
docs: // Release 释放连接池中所有连接