change AEAD interface to return bytes.Reader instead of io.Reader

crypto/AEAD.go

@@ -1,8 +1,11 @@
 package crypto
 
-import "io"
+import (
+	"bytes"
+	"io"
+)
 
 // An AEAD implements QUIC's authenticated encryption and associated data
 type AEAD interface {
-	Open(associatedData []byte, ciphertext io.Reader) (io.Reader, error)
+	Open(associatedData []byte, ciphertext io.Reader) (*bytes.Reader, error)
 }