Make log keys configurable. (#176)

Update example to take advantage of new log endpoint middleware.

example/weather/services/forecaster/cmd/forecaster/main.go

@@ -76,6 +76,7 @@ func main() {
 	// 5. Create service & endpoints
 	svc := forecaster.New(wc)
 	endpoints := genforecaster.NewEndpoints(svc)
+	endpoints.Use(log.Endpoint)
 
 	// 6. Create transport
 	server := gengrpc.New(endpoints, nil)

example/weather/services/front/cmd/front/main.go

@@ -101,6 +101,7 @@ func main() {
 	// 4. Create service & endpoints
 	svc := front.New(fc, lc)
 	endpoints := genfront.NewEndpoints(svc)
+	endpoints.Use(log.Endpoint)
 
 	// 5. Create transport
 	mux := goahttp.NewMuxer()

example/weather/services/locator/cmd/locator/main.go

@@ -76,6 +76,7 @@ func main() {
 	// 5. Create service & endpoints
 	svc := locator.New(ipc)
 	endpoints := genlocator.NewEndpoints(svc)
+	endpoints.Use(log.Endpoint)
 
 	// 6. Create transport
 	server := gengrpc.New(endpoints, nil)

log/http.go

@@ -67,10 +67,10 @@ func HTTP(logCtx context.Context, opts ...HTTPLogOption) func(http.Handler) http
 func Endpoint(e goa.Endpoint) goa.Endpoint {
 	return func(ctx context.Context, req interface{}) (interface{}, error) {
 		if s := ctx.Value(goa.ServiceKey); s != nil {
-			ctx = With(ctx, KV{K: "goa.service", V: s})
+			ctx = With(ctx, KV{K: GoaServiceKey, V: s})
 		}
 		if m := ctx.Value(goa.MethodKey); m != nil {
-			ctx = With(ctx, KV{K: "goa.method", V: m})
+			ctx = With(ctx, KV{K: GoaMethodKey, V: m})
 		}
 		return e(ctx, req)
 	}

log/keys.go

@@ -18,4 +18,6 @@ var (
 	GRPCCodeKey     = "grpc.code"
 	GRPCStatusKey   = "grpc.status"
 	GRPCDurationKey = "grpc.time_ms"
+	GoaServiceKey   = "goa.service"
+	GoaMethodKey    = "goa.method"
 )