[MM-19473] Fix data race on user login (#12870)

* Avoid writes to App.Session outside the app layer

* Fix merge

* Remove unneeded else condition

go.mod

@@ -52,6 +52,8 @@ require (
 	github.com/miekg/dns v1.1.19 // indirect
 	github.com/minio/minio-go/v6 v6.0.38
 	github.com/mitchellh/go-testing-interface v1.0.0 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.1 // indirect
 	github.com/muesli/smartcrop v0.3.0 // indirect
 	github.com/olekukonko/tablewriter v0.0.1 // indirect
 	github.com/onsi/ginkgo v1.8.0 // indirect