Fix returning null from KerberosUsernameProvider.GetUsername with concurrent calls (#6137)

vonzshik · vonzshik · commit 9b9ca5533f29 · 2025-06-20T13:22:01.000+03:00
Fixes #6136 (cherry picked from commit e3921f2)
diff --git a/src/Npgsql/KerberosUsernameProvider.cs b/src/Npgsql/KerberosUsernameProvider.cs
@@ -11,9 +11,9 @@ namespace Npgsql;
 /// Launches MIT Kerberos klist and parses out the default principal from it.
 /// Caches the result.
 /// </summary>
-sealed class KerberosUsernameProvider
+static class KerberosUsernameProvider
 {
-    static bool _performedDetection;
+    static volatile bool _performedDetection;
     static string? _principalWithRealm;
     static string? _principalWithoutRealm;
 
