.

go/internal/xio/xio.go

@@ -83,15 +83,20 @@ func LClose(ctx context.Context, c io.Closer) {
 // WithCloseOnErrCancel closes c on ctx cancel while f is run, or if f returns with an error.
 //
 // It is usually handy to propagate cancellation to interrupt IO.
+//
+// Returned error is what f returned, or ctx.Err() if f retrned nil despite that
+// ctx was canceled and c closed.
 func WithCloseOnErrCancel(ctx context.Context, c io.Closer, f func() error) (err error) {
 	closed := false
 	fdone := make(chan error)
 	defer func() {
-		errf, ok := <-fdone // wait for f to complete	XXX return f's error
+		errf, ok := <-fdone // wait for f to complete
 		if ok {
 			// it was ctx cancel and `return ctx.Err()` vvv
-			// -> change return to be what f returned
-			err = errf
+			// -> change return to be what f returned if !nil
+			if errf != nil {
+				err = errf
+			}
 		}
 
 		if err != nil {
@@ -124,17 +129,15 @@ func WithCloseOnErrCancel(ctx context.Context, c io.Closer, f func() error) (err
 //
 // It is usually handy to propagate cancellation to interrupt IO.
 func WithCloseOnRetCancel(ctx context.Context, c io.Closer, f func() error) error {
-	var errf error
 	err := WithCloseOnErrCancel(ctx, c, func() error {
-		errf = f()
-		e := errf
+		e := f()
 		if e == nil {
 			e = retOK // force c close
 		}
 		return e
 	})
 	if err == retOK {
-		err = errf
+		err = nil
 	}
 	return err
 }

go/neo/neonet/newlink.go

@@ -135,6 +135,9 @@ func _handshakeClient(ctx context.Context, conn net.Conn, version uint32, encPre
 		return nil
 	})
 	if err != nil {
+		if ctx.Err() != nil {
+			err = ctx.Err() // error was due to ctx cancel
+		}
 		return 0, nil, err
 	}
 
@@ -179,6 +182,9 @@ func _handshakeServer(ctx context.Context, conn net.Conn, version uint32) (enc p
 		return nil
 	})
 	if err != nil {
+		if ctx.Err() != nil {
+			err = ctx.Err() // error was due to ctx cancel
+		}
 		return 0, nil, err
 	}