tech(alerting): change from array to map

pkg/services/sqlstore/alert_heartbeat_test.go

@@ -0,0 +1,18 @@
+package sqlstore
+
+import (
+	"testing"
+
+	//	m "github.com/grafana/grafana/pkg/models"
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestAlertingHeartbeatDataAccess(t *testing.T) {
+
+	Convey("Testing Alerting data access", t, func() {
+		InitTestDB(t)
+		//send heartbeat from server 1
+		//send heartbeat from server 2
+
+	})
+}