func withDeadline(parent context.Context, deadline time.Time) (context.Context, context.CancelFunc) {
	if deadline.IsZero() {
		return parent, func() {}
	}
	return context.WithDeadline(parent, deadline)
}
func withDeadline(parent context.Context, deadline time.Time) (context.Context, context.CancelFunc) {
	if deadline.IsZero() {
		return parent, func() {}
	}
	return context.WithDeadline(parent, deadline)
}
func withDeadline ( parent context . Context , deadline time . Time ) ( context . Context , context . CancelFunc ) { if deadline . IsZero ( ) { return parent , func ( ) { } } return context . WithDeadline ( parent , deadline ) }
// withDeadline is like context.WithDeadline, except it ignores the zero deadline.
withDeadline is like context . WithDeadline except it ignores the zero deadline .