feat(config): add default transport option

config/config.go

@@ -23,6 +23,7 @@ var (
 type Config struct {
 	transports         map[string]Transport
 	transportFactories map[string]TransportFactory
+	defaultTransport   string
 	opts               []postdog.Option
 }
 
@@ -44,6 +45,7 @@ type TransportFactory interface {
 type TransportFactoryFunc func(context.Context, map[string]interface{}) (postdog.Transport, error)
 
 type rawConfig struct {
+	Default    string               `yaml:"default"`
 	Transports map[string]Transport `yaml:"transports"`
 }
 
@@ -91,6 +93,7 @@ func (cfg *Config) Parse(raw []byte) error {
 		return fmt.Errorf("unmarshal yaml: %w", err)
 	}
 	cfg.transports = rawCfg.Transports
+	cfg.defaultTransport = rawCfg.Default
 	return nil
 }
 
@@ -133,8 +136,13 @@ func (cfg *Config) Dog(ctx context.Context, opts ...Option) (*postdog.Dog, error
 	}
 
 	dogOpts = append(dogOpts, cfg.opts...)
+	dog := postdog.New(dogOpts...)
 
-	return postdog.New(dogOpts...), nil
+	if cfg.defaultTransport != "" {
+		dog.Use(cfg.defaultTransport)
+	}
+
+	return dog, nil
 }
 
 // Transport accepts the transport-specific configuration and instantiates a transport from that configuration.

config/config_test.go

@@ -178,6 +178,50 @@ func TestConfig(t *testing.T) {
 					})
 				})
 			}))
+
+			Convey("Given a configuration with a default transport", WithParsedConfig("./testdata/with_default.yml", func(cfg *config.Config) {
+				Convey("When I instantiate postdog.Dog and provide the config.TransportFactories", func() {
+					factory1 := mock_config.NewMockTransportFactory(ctrl)
+					mockTransport1 := mock_postdog.NewMockTransport(ctrl)
+					factory1.EXPECT().
+						Transport(gomock.Any(), map[string]interface{}{
+							"key1": 1,
+							"key2": map[string]interface{}{
+								"key2.1": "val2.1",
+								"key2.2": "val2.2",
+							},
+						}).
+						Return(mockTransport1, nil)
+
+					factory2 := mock_config.NewMockTransportFactory(ctrl)
+					mockTransport2 := mock_postdog.NewMockTransport(ctrl)
+					factory2.EXPECT().
+						Transport(gomock.Any(), map[string]interface{}{
+							"key1": map[string]interface{}{
+								"key1.1": "val1.1",
+								"key1.2": "val1.2",
+							},
+							"key2": 2,
+						}).
+						Return(mockTransport2, nil)
+
+					dog, err := cfg.Dog(
+						context.Background(),
+						config.WithTransportFactory("trans1", factory1),
+						config.WithTransportFactory("trans2", factory2),
+					)
+
+					Convey("It shouldn't fail", func() {
+						So(err, ShouldBeNil)
+					})
+
+					Convey("dog should use the specified default transport", func() {
+						tr, err := dog.Transport("")
+						So(err, ShouldBeNil)
+						So(tr, ShouldEqual, mockTransport2)
+					})
+				})
+			}))
 		})
 	})
 }

config/testdata/with_default.yml

@@ -0,0 +1,17 @@
+default: test2
+
+transports:
+  test1:
+    use: trans1
+    config:
+      key1: 1
+      key2:
+        key2.1: val2.1
+        key2.2: val2.2
+  test2:
+    use: trans2
+    config:
+      key1:
+        key1.1: val1.1
+        key1.2: val1.2
+      key2: 2