Upgrade golangci-lint and fixes some linting errors. (#22909)

Example: https://play.golang.org/p/cfPIPG3BwjJ

pkg/services/sqlstore/session.go

@@ -28,7 +28,7 @@ func newSession() *DBSession {
 }
 
 func startSession(ctx context.Context, engine *xorm.Engine, beginTran bool) (*DBSession, error) {
-	value := ctx.Value(ContextSessionName)
+	value := ctx.Value(ContextSessionKey{})
 	var sess *DBSession
 	sess, ok := value.(*DBSession)
 

pkg/services/sqlstore/sqlstore.go

@@ -35,7 +35,8 @@ var (
 	sqlog log.Logger = log.New("sqlstore")
 )
 
-const ContextSessionName = "db-session"
+// ContextSessionKey is used as key to save values in `context.Context`
+type ContextSessionKey struct{}
 
 func init() {
 	// This change will make xorm use an empty default schema for postgres and

pkg/services/sqlstore/transactions.go

@@ -22,7 +22,7 @@ func (ss *SqlStore) InTransaction(ctx context.Context, fn func(ctx context.Conte
 
 func (ss *SqlStore) inTransactionWithRetry(ctx context.Context, fn func(ctx context.Context) error, retry int) error {
 	return inTransactionWithRetryCtx(ctx, ss.engine, func(sess *DBSession) error {
-		withValue := context.WithValue(ctx, ContextSessionName, sess)
+		withValue := context.WithValue(ctx, ContextSessionKey{}, sess)
 		return fn(withValue)
 	}, retry)
 }

pkg/services/sqlstore/transactions_test.go

@@ -15,7 +15,7 @@ var ErrProvokedError = errors.New("testing error")
 func TestTransaction(t *testing.T) {
 	ss := InitTestDB(t)
 
-	Convey("InTransaction asdf asdf", t, func() {
+	Convey("InTransaction", t, func() {
 		cmd := &models.AddApiKeyCommand{Key: "secret-key", Name: "key", OrgId: 1}
 
 		err := AddApiKey(cmd)

pkg/services/sqlstore/user_test.go

@@ -455,8 +455,8 @@ func TestUserDataAccess(t *testing.T) {
 			var err error
 			createUserCmd := &models.CreateUserCommand{
 				Email:   fmt.Sprint("admin", "@test.com"),
-				Name:    fmt.Sprint("admin"),
-				Login:   fmt.Sprint("admin"),
+				Name:    "admin",
+				Login:   "admin",
 				IsAdmin: true,
 			}
 			err = CreateUser(context.Background(), createUserCmd)