fix(GODT-2412): Don't treat context cancellation as BadEvent

internal/errors.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2023 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package internal
+
+import "errors"
+
+// ErrCause returns the cause of the error, the inner-most error in the wrapped chain.
+func ErrCause(err error) error {
+	cause := err
+
+	for errors.Unwrap(cause) != nil {
+		cause = errors.Unwrap(cause)
+	}
+
+	return cause
+}