Fix syntax

Author: Pancake Team

Makefile

@@ -1,5 +1,7 @@
 instance_id = $(shell curl "http://10.1.9.49:4001/api/instance_id?name=cakecloud-db&project_name=${project}")
 hostname = $(shell hostname)
+DATA_SOURCE_NAME="postgresql://${database_user}:${database_password}@localhost:${port}/${database_name}"
+PG_EXPORTER_CONSTANT_LABELS="domain=${instance_id}_${hostname}"
 
 all: prepare_files save_env_vars start_service
 
@@ -9,10 +11,8 @@ prepare_files:
 	sudo cp -r ./cakecloud-postgres-exporter.service /etc/systemd/system/
 
 save_env_vars:
-	DATA_SOURCE_NAME="postgresql://${database_user}:${database_password}@localhost:${port}/${database_name}"
-	echo $(DATA_SOURCE_NAME) >> vars/DATA_SOURCE_NAME
-	PG_EXPORTER_CONSTANT_LABELS="domain=${instance_id}_${hostname}"
-	echo $(PG_EXPORTER_CONSTANT_LABELS) >> vars/PG_EXPORTER_CONSTANT_LABELS
+	echo $(DATA_SOURCE_NAME) > vars/DATA_SOURCE_NAME
+	echo $(PG_EXPORTER_CONSTANT_LABELS) > vars/PG_EXPORTER_CONSTANT_LABELS
 
 start:
 	export DATA_SOURCE_NAME=$(shell cat ./vars/DATA_SOURCE_NAME); \