code: func (c *Client) callOnTokenRenewHandlers(token string) {
  	c.m.RLock()
  	defer c.m.RUnlock()
  
  	for _, handler := range c.onTokenRenewHandlers {
  		func() {
  			defer nopRecover()
  			handler(token)
  		}()
  	}
  }
docs: // callOnTokenRenewHandlers calls all registered functions when
  // we successfully obtain new token from kontrol.