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>

utils/utils.go

@@ -4,12 +4,13 @@
 package utils
 
 import (
-	"github.com/pkg/errors"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"net/url"
 	"strings"
+
+	"github.com/pkg/errors"
 )
 
 func StringInSlice(a string, slice []string) bool {