Move documentation to init.go

antireplay/doc.go

-// Antireplay package has cache implementations that are effective
-// against replay attacks.
-//
-// To understand more about replay attacks, please read documentation
-// for mtglib.AntiReplayCache interface. This package has a list of some
-// implementations of this interface.
-package antireplay

antireplay/init.go

+// Antireplay package has cache implementations that are effective
+// against replay attacks.
+//
+// To understand more about replay attacks, please read documentation
+// for mtglib.AntiReplayCache interface. This package has a list of some
+// implementations of this interface.
 package antireplay
 
 const (