code: func IsKeyJustReleased(key ebiten.Key) bool {
  	theInputState.m.RLock()
  	r := theInputState.keyDurations[key] == 0 && theInputState.prevKeyDurations[key] > 0
  	theInputState.m.RUnlock()
  	return r
  }
docs: // IsKeyJustReleased returns a boolean value indicating
  // whether the given key is released just in the current frame.
  //
  // IsKeyJustReleased is concurrent safe.