code: func (g *Game) Resign(color Color) {
  	if g.outcome != NoOutcome || color == NoColor {
  		return
  	}
  	if color == White {
  		g.outcome = BlackWon
  	} else {
  		g.outcome = WhiteWon
  	}
  	g.method = Resignation
  }
docs: // Resign resigns the game for the given color.  If the game has
  // already been completed then the game is not updated.