Some nitpicking

codec/codec.go

@@ -16,8 +16,11 @@ type MessageType int
 // Takes in a connection/buffer and returns a new Codec
 type NewCodec func(io.ReadWriteCloser) Codec
 
-// Codec encodes/decodes various types of
-// messages used within go-micro
+// Codec encodes/decodes various types of messages used within go-micro.
+// ReadHeader and ReadBody are called in pairs to read requests/responses
+// from the connection. Close is called when finished with the
+// connection. ReadBody may be called with a nil argument to force the
+// body to be read and discarded.
 type Codec interface {
 	ReadHeader(*Message, MessageType) error
 	ReadBody(interface{}) error