Reduce unit test time

Makefile

@@ -654,11 +654,11 @@ cover_profile:
 	$Q echo Running special test cases without race detector:
 	$Q go test ./cmd/server/cadence/
 	$Q echo Running package tests:
-	$Q for dir in $(PKG_TEST_DIRS); do \
-		mkdir -p $(BUILD)/"$$dir"; \
-		go test "$$dir" $(TEST_ARG) -coverprofile=$(BUILD)/"$$dir"/coverage.out || exit 1; \
-		(cat $(BUILD)/"$$dir"/coverage.out | grep -v "^mode: \w\+" >> $(UNIT_COVER_FILE)) || true; \
-	done;
+	$Q echo $(PKG_TEST_DIRS) | tr ' ' '\n' | xargs -P $(shell nproc) -I {} sh -c \
+		'mkdir -p $(BUILD)/"{}" && go test "{}" $(TEST_ARG) -coverprofile=$(BUILD)/"{}"/coverage.out || exit 1'
+	$Q echo Merging coverage profiles:
+	$Q find $(BUILD) -name coverage.out | xargs cat | grep -v "^mode:" >> $(UNIT_COVER_FILE)
+
 
 cover_integration_profile:
 	$Q mkdir -p $(BUILD)