public class KeyInputHandler {
    private static final Logger LOGGER = LogManager.getLogger();

    @SubscribeEvent
    public void onKeyInput(InputEvent.KeyInputEvent event)
    {
        PlayerEntity player = Minecraft.getInstance().player;
        if (Keybinds.test_item_gui_key.isPressed() && player.getHeldItemMainhand().getItem() instanceof ItemTestItem){
            LOGGER.info("KEY PRESSED");

        }
    }
}

How can I open my ItemTestItem's GUI when I press the C key?
Right Now I am opening it from NetworkHooks in my ItemTestItem class.

@Nonnull
@Override
public ActionResult<ItemStack> onItemRightClick(World world, PlayerEntity player, Hand handIn) {
    ItemStack stack = player.getHeldItem(handIn).getStack();
    if (!world.isRemote){
        if (player.isSneaking()){
            INamedContainerProvider containerProviderTestItem = new ContainerProviderTestItem(this, stack);
            final int NUMBER_OF_SLOTS = 8;
            NetworkHooks.openGui((ServerPlayerEntity) player, containerProviderTestItem, (packetBuffer)-> packetBuffer.writeInt(NUMBER_OF_SLOTS);});
            return ActionResult.resultSuccess(stack);
      	}
    }
}

Here's the git repo if needed: https://github.com/NindyBun/TestMod/blob/master/src/main/java/com/nindybun/miningtool/KeyInputHandler.java
Apologies in advance if my code is crude.

Actually, nvm I got it.