code: func (c *Call) WaitUntil(w <-chan time.Time) *Call {
  	c.lock()
  	defer c.unlock()
  	c.WaitFor = w
  	return c
  }
docs: // WaitUntil sets the channel that will block the mock's return until its closed
  // or a message is received.
  //
  //    Mock.On("MyMethod", arg1, arg2).WaitUntil(time.After(time.Second))