add workaround and test for workaround

.gitignore

@@ -0,0 +1 @@
+cover.out

Makefile

@@ -0,0 +1,15 @@
+.PHONY: deps workaround
+
+deps:
+	go get github.com/wadey/gocovmerge
+
+workaround: deps
+	@echo Running tests
+	$(eval PKGS := $(shell go list ./... | grep -v /vendor/))
+	$(eval PKGS_DELIM := $(shell echo $(PKGS) | sed -e 's/ /,/g'))
+	go list -f '{{if or (len .TestGoFiles) (len .XTestGoFiles)}}go test -test.v -covermode=count -coverprofile={{.Name}}_{{len .Imports}}_{{len .Deps}}.coverprofile -coverpkg $(PKGS_DELIM) {{.ImportPath}}{{end}}' $(PKGS) | xargs -I {} bash -c {}
+	gocovmerge `ls *.coverprofile` > cover.out
+	rm *.coverprofile
+
+testworkaround: workaround
+	diff -u cover.out cover.ok

README.md

@@ -35,3 +35,13 @@ of cource, we can produce html, and can confirm 100% lines are coverd.
 ```sh
 $ go tool cover -html=coverage.out
 ```
+
+### workaround using gocovmerge
+
+- https://github.com/wadey/gocovmerge
+- https://github.com/golang/go/issues/6909#issuecomment-233493644
+
+```
+make workaround
+make testworkaround
+```

cover.ok

@@ -0,0 +1,6 @@
+mode: count
+github.com/haya14busa/go-cover-multi-pkgs-example/root.go:5.24,7.2 1 1
+github.com/haya14busa/go-cover-multi-pkgs-example/root.go:9.17,12.2 2 1
+github.com/haya14busa/go-cover-multi-pkgs-example/sub/sub.go:3.23,5.2 1 1
+github.com/haya14busa/go-cover-multi-pkgs-example/sub/sub.go:7.24,9.2 1 1
+github.com/haya14busa/go-cover-multi-pkgs-example/sub/sub.go:11.30,13.2 1 2