Handle signal exits after walker close

Record whether the walker command returned after its context was
canceled.

Treat those wait errors as expected during Close so platforms that
report cancellation as signal termination do not fail the unblock test.

Author: tobim

walk/path_stream.go

@@ -37,8 +37,9 @@ type PathStreamReader struct {
 	eg      *errgroup.Group
 	scanner *bufio.Scanner
 
-	waitMu  sync.Mutex
-	waitErr error
+	waitMu       sync.Mutex
+	waitErr      error
+	waitCanceled bool
 }
 
 func (p *PathStreamReader) Read(ctx context.Context, files []*File) (n int, err error) {
@@ -153,7 +154,7 @@ func (p *PathStreamReader) Close() error {
 	p.waitMu.Lock()
 	defer p.waitMu.Unlock()
 
-	if p.waitErr != nil && !errors.Is(p.waitErr, context.Canceled) {
+	if p.waitErr != nil && !errors.Is(p.waitErr, context.Canceled) && !p.waitCanceled {
 		return fmt.Errorf("failed to wait for %s command to complete: %w", p.cfg.Name, p.waitErr)
 	}
 
@@ -252,6 +253,7 @@ func NewPathStreamReader(
 
 		reader.waitMu.Lock()
 		reader.waitErr = err
+		reader.waitCanceled = ctx.Err() != nil
 		reader.waitMu.Unlock()
 
 		closeErr := stdoutW.Close()