goimports (#16640)

* format using `goimports -local github.com/mattermost/mattermost-server/v5 -w`

* added goimports lint check to .golangci.yml

* format using `goimports -local github.com/mattermost/mattermost-server/v5 -w` for a corner case

* make app-layers, *-mocks and store-layers for ci check

Co-authored-by: Mahmudul Haque <mahmudulhaque@protonmail.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

services/mailservice/mail.go

@@ -10,15 +10,14 @@ import (
 	"io"
 	"mime"
 	"net"
+	"net/http"
 	"net/mail"
 	"net/smtp"
 	"time"
 
+	"github.com/jaytaylor/html2text"
 	gomail "gopkg.in/mail.v2"
 
-	"net/http"
-
-	"github.com/jaytaylor/html2text"
 	"github.com/mattermost/mattermost-server/v5/mlog"
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/services/filesstore"

services/mailservice/mail_test.go

@@ -10,20 +10,20 @@ import (
 	"io"
 	"io/ioutil"
 	"net"
+	"net/mail"
+	"net/smtp"
 	"os"
 	"strings"
 	"testing"
 	"time"
 
-	"net/mail"
-	"net/smtp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/mattermost/mattermost-server/v5/config"
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/services/filesstore"
 	"github.com/mattermost/mattermost-server/v5/utils"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestMailConnectionFromConfig(t *testing.T) {