test: supplement the unit testing of transport/grpc (#2371)

* test:grpc codec test

* style:go fmt

* refactor:delete useless code

* style:go fmt

transport/grpc/codec_test.go

@@ -0,0 +1,28 @@
+package grpc
+
+import (
+	"reflect"
+	"testing"
+
+	"google.golang.org/protobuf/types/known/structpb"
+)
+
+func TestCodec(t *testing.T) {
+	in, err := structpb.NewStruct(map[string]interface{}{"Golang": "Kratos"})
+	if err != nil {
+		t.Errorf("grpc codec create input data error:%v", err)
+	}
+	c := codec{}
+	data, err := c.Marshal(in)
+	if err != nil {
+		t.Errorf("grpc codec marshal error:%v", err)
+	}
+	out := &structpb.Struct{}
+	err = c.Unmarshal(data, out)
+	if err != nil {
+		t.Errorf("grpc codec unmarshal error:%v", err)
+	}
+	if !reflect.DeepEqual(in, out) {
+		t.Errorf("grpc codec want %v, got %v", in, out)
+	}
+}