Support coverage report.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

docker/testing.sh

@@ -9,4 +9,6 @@ sed -i"" -e "s/localhost/redis/g" config/config.go
 sed -i"" -e "s/localhost/redis/g" config/config_test.go
 sed -i"" -e "s/localhost/redis/g" gorush/status_test.go
 sed -i"" -e "s/localhost/redis/g" storage/redis/redis_test.go
-make install && make test
+make install
+make coverage
+make report