Set the -race flag for go tests

Makefile

@@ -1,5 +1,8 @@
 .PHONY: build build_examples install_examples lint lint-copyright lint-golang
 
+GO_TEST_FLAGS=-race
+GO_TEST=go test ${GO_TEST_FLAGS}
+
 build:
 	go build ./...
 
@@ -8,13 +11,13 @@ test: test_unit test_examples
 
 .PHONY: test_unit
 test_unit: build
-	go test ./...
-	cd infer/tests && go test ./...
-	cd integration && go test ./...
-	cd resourcex && go test ./...
-	cd tests && go test ./...
+	${GO_TEST} ./...
+	cd infer/tests && ${GO_TEST} ./...
+	cd integration && ${GO_TEST} ./...
+	cd resourcex && ${GO_TEST} ./...
+	cd tests && ${GO_TEST} ./...
 	for d in examples/*; do if [ -d $$d ]; then \
-		cd $$d; go test ./... || exit $$?; \
+		cd $$d; ${GO_TEST} ./... || exit $$?; \
 	cd -; fi; done
 
 lint: lint-golang lint-copyright