Ok so basically i coded a mod that should play with some packets for custom servers. it should allow to use spigot plugins with some commands on forge to display custom buttons and more.

but i got an error:

[22:36:34] [main/WARN] [mixin/]: Reference map 'spigot.conv.mixin-refmap.json' for spigot.conv.mixin.json could not be read. If this is a development environment you can ignore this message
22:36:35.506
[22:36:35] [main/FATAL] [mixin/]: Mixin apply failed spigot.conv.mixin.json:NetworkHandlerMixin -> net.minecraft.network.NetworkManager: org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException Critical injection failure: @Inject annotation on onSendPacket could not find any targets matching 'sendPacket(Lnet/minecraft/network/IPacket;)V' in net.minecraft.network.NetworkManager. No refMap loaded. [PREINJECT Applicator Phase -> spigot.conv.mixin.json:NetworkHandlerMixin -> Prepare Injections ->  -> handler$zza000$onSendPacket(Lnet/minecraft/network/IPacket;Lorg/spongepowered/asm/mixin/injection/callback/CallbackInfo;)V -> Parse]
22:36:35.506
org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException: Critical injection failure: @Inject annotation on onSendPacket could not find any targets matching 'sendPacket(Lnet/minecraft/network/IPacket;)V' in net.minecraft.network.NetworkManager. No refMap loaded. [PREINJECT Applicator Phase -> spigot.conv.mixin.json:NetworkHandlerMixin -> Prepare Injections ->  -> handler$zza000$onSendPacket(Lnet/minecraft/network/IPacket;Lorg/spongepowered/asm/mixin/injection/callback/CallbackInfo;)V -> Parse]
22:36:35.507
at org.spongepowered.asm.mixin.injection.struct.InjectionInfo.findMethods(InjectionInfo.java:572) ~[mixin-0.8.2.jar:0.8.2+unknown-b0.git-unknown] {}
22:36:35.507
at org.spongepowered.asm.mixin.injection.struct.InjectionInfo.readAnnotation(InjectionInfo.java:288) ~[mixin-0.8.2.jar:0.8.2+unknown-b0.git-unknown] {}

you don't understand. i made a spigot api to send custom packets to my forge mod so i can display custom gui's and mod. but i ended up just removing the refamp.. with some more tricks it ended up running without crashing.