do not try to decode empty slice

client.go

@@ -41,18 +41,20 @@ func (c *ClientCodec) WriteRequest(r *rpc.Request, body interface{}) error {
 	// writeServiceMethod to the buffer
 	buf.WriteString(r.ServiceMethod)
 	// Initialize gob
-	enc := gob.NewEncoder(buf)
-	// write data to the gob
-	err := enc.Encode(body)
-	if err != nil {
-		return errors.E(op, err)
+	if body != nil {
+		enc := gob.NewEncoder(buf)
+		// write data to the gob
+		err := enc.Encode(body)
+		if err != nil {
+			return errors.E(op, err)
+		}
 	}
 
 	frame.WritePayloadLen(uint32(buf.Len()))
 	frame.WritePayload(buf.Bytes())
 	frame.WriteCRC()
 
-	err = c.relay.Send(frame)
+	err := c.relay.Send(frame)
 	if err != nil {
 		return errors.E(op, err)
 	}

decoders.go

@@ -14,18 +14,26 @@ func decodeJSON(out interface{}, frame *Frame) error {
 	if len(opts) != 2 {
 		return errors.E(op, errors.Str("should be 2 options. SEQ_ID and METHOD_LEN"))
 	}
-	return json.Unmarshal(frame.Payload()[opts[1]:], out)
+	payload := frame.Payload()[opts[1]:]
+	if len(payload) == 0 {
+		return nil
+	}
+	return json.Unmarshal(payload, out)
 }
 
 func decodeGob(out interface{}, frame *Frame) error {
 	const op = errors.Op("client: decode GOB")
-	buf := new(bytes.Buffer)
-	dec := gob.NewDecoder(buf)
 	opts := frame.ReadOptions()
 	if len(opts) != 2 {
 		return errors.E(op, errors.Str("should be 2 options. SEQ_ID and METHOD_LEN"))
 	}
 	payload := frame.Payload()[opts[1]:]
+	if len(payload) == 0 {
+		return nil
+	}
+
+	buf := new(bytes.Buffer)
+	dec := gob.NewDecoder(buf)
 	buf.Write(payload)
 
 	return dec.Decode(out)
@@ -38,6 +46,9 @@ func decodeRaw(out interface{}, frame *Frame) error {
 		return errors.E(op, errors.Str("should be 2 options. SEQ_ID and METHOD_LEN"))
 	}
 	payload := frame.Payload()[opts[1]:]
+	if len(payload) == 0 {
+		return nil
+	}
 
 	if raw, ok := out.(*[]byte); ok {
 		*raw = append(*raw, payload...)
@@ -54,5 +65,9 @@ func decodeMsgPack(out interface{}, frame *Frame) error {
 		return errors.E(op, errors.Str("should be 2 options. SEQ_ID and METHOD_LEN"))
 	}
 	payload := frame.Payload()[opts[1]:]
+	if len(payload) == 0 {
+		return nil
+	}
+
 	return msgpack.Unmarshal(payload, out)
 }