drpcmanager: cancel stream with error when terminated

Terminations were canceling streams with `context.Canceled` instead
of surfacing the error, causing unexpected behavior.

drpcmanager/manager.go

@@ -291,7 +291,8 @@ func (m *Manager) manageStream(ctx context.Context, stream *drpcstream.Stream) {
 
 	select {
 	case <-m.sigs.term.Signal():
-		stream.Cancel(context.Canceled)
+		err, _ := m.sigs.term.Get()
+		stream.Cancel(err)
 		<-m.sterm
 		return
 

internal/integration/transport_test.go

@@ -5,6 +5,8 @@ package integration
 
 import (
 	"context"
+	"errors"
+	"io"
 	"testing"
 
 	"github.com/zeebo/assert"
@@ -111,6 +113,6 @@ func TestTransport_ErrorCausesCancel(t *testing.T) {
 	assert.NoError(t, cli.DRPCConn().(*drpcconn.Conn).Transport().Close())
 
 	// ensure both of the errors we sent are canceled
-	assert.Equal(t, <-errs, context.Canceled)
-	assert.Equal(t, <-errs, context.Canceled)
+	assert.True(t, errors.Is(<-errs, io.ErrClosedPipe))
+	assert.True(t, errors.Is(<-errs, io.EOF))
 }