feat: add golangci-lint for go linting

internal/service/auth_service.go

@@ -845,10 +845,3 @@ func (auth *AuthService) ClearRateLimitsTestingOnly() {
 	}
 	auth.loginMutex.Unlock()
 }
-
-func (auth *AuthService) getCookieDomain() string {
-	if auth.config.SubdomainsEnabled {
-		return "." + auth.config.CookieDomain
-	}
-	return auth.config.CookieDomain
-}

internal/service/ldap_service.go

@@ -269,7 +269,7 @@ func (ldap *LdapService) reconnect() error {
 	exp.Reset()
 
 	operation := func() (*ldapgo.Conn, error) {
-		ldap.conn.Close()
+		ldap.conn.Close() //nolint:errcheck
 		conn, err := ldap.connect()
 		if err != nil {
 			return nil, err

internal/service/oauth_extractors.go

@@ -92,7 +92,7 @@ func simpleReq[T any](client *http.Client, url string, headers map[string]string
 	if err != nil {
 		return nil, err
 	}
-	defer res.Body.Close()
+	defer res.Body.Close() //nolint:errcheck
 
 	if res.StatusCode < 200 || res.StatusCode >= 300 {
 		return nil, fmt.Errorf("request failed with status: %s", res.Status)