[v11.0.x] PostgreSQL: Fix the verify-ca mode (#85775)

PostgreSQL: Fix the verify-ca mode (#85530)

postgres: fix the verify-ca problem
(cherry picked from commit 8a15ed42ae)

Co-authored-by: Gábor Farkas <gabor.farkas@gmail.com>

pkg/tsdb/grafana-postgresql-datasource/postgres.go

@@ -224,6 +224,14 @@ func (s *Service) generateConnectionString(dsInfo sqleng.DataSourceInfo) (string
 
 	connStr += fmt.Sprintf(" sslmode='%s'", escape(tlsSettings.Mode))
 
+	// there is an issue with the lib/pq module, the `verify-ca` tls mode
+	// does not work correctly. ( see https://github.com/lib/pq/issues/1106 )
+	// to workaround the problem, if the `verify-ca` mode is chosen,
+	// we disable sslsni.
+	if tlsSettings.Mode == "verify-ca" {
+		connStr += " sslsni=0"
+	}
+
 	// Attach root certificate if provided
 	if tlsSettings.RootCertFile != "" {
 		logger.Debug("Setting server root certificate", "tlsRootCert", tlsSettings.RootCertFile)