Hello. I wanna say special thanks to @kawaiinekololis.
go to 1.8.9-Forge/1.12.2-Forge and go to src/main/resources/ then find liquidbounce_at.cfg
If you are using 1.12.2, add this line:
# CPacketKeepAlive public net.minecraft.network.play.client.CPacketKeepAlive field_149461_a # key
then it will look like that.
If you are using 1.8.9, do as 1.12.2, but change CPacketKeepAlive to C00PacketKeepAlive
Profit! Now you can change key to your value.