code: func (c *chainView) Height() int32 {
  	c.mtx.Lock()
  	height := c.height()
  	c.mtx.Unlock()
  	return height
  }
docs: // Height returns the height of the tip of the chain view.  It will return -1 if
  // there is no tip (which only happens if the chain view has not been
  // initialized).
  //
  // This function is safe for concurrent access.