In kapitel05/main.go

accept := request.Header.Get("Accept")
switch accept {
	case "application/pdf":
		content := bytes.NewReader(i.ToPDF())
		http.ServeContent(writer, request, "invoice.pdf", time.Now(), content)
	case "application/json":
		b, _ := json.Marshal(i)
		writer.Header().Set("Content-Type", "application/json")
		_, _ = writer.Write(b)
	default:
		writer.WriteHeader(http.StatusNotAcceptable)
	}

If the client sends multiple values curl -i http://localhost:8080/customers/1/invoices/1 \ -H 'Accept: application/pdf, application/json' then the switch will always hit the default case.

Value of accept is application/pdf, application/json and does not match any case.

I thought I'd mention it as the book states that query on page 65

The code smells mentioned in the book on page 84 are not addressed in chapter 7.

Should the aggregation block be refactored into a separate function on the usecase or the invoice domain? What is your take on that?

go get github.com/gorilla/mux produziert einen Fehler.

mit go get -u github.com/gorilla/mux funktioniert es einwandfrei