add db.out tag

Author: keisku

Diff for: contrib/valkey-go/valkey.go

@@ -187,6 +187,7 @@ func (c *coreClient) buildStartSpanOptions(input buildStartSpanOptionsInput) []t
 		tracer.Tag(ext.SpanKind, ext.SpanKindClient),
 		tracer.Tag(ext.DBSystem, ext.DBSystemValkey),
 		tracer.Tag(ext.ValkeyDatabaseIndex, c.option.SelectDB),
+		tracer.Tag("db.out", c.option.SelectDB),
 	}
 	opts = append(opts, c.peerTags()...)
 	if input.command != "" {

Diff for: contrib/valkey-go/valkey_test.go

@@ -336,6 +336,8 @@ func TestNewClient(t *testing.T) {
 				assert.Equal(t, "127.0.0.1", span.Tag(ext.TargetHost))
 				assert.Equal(t, valkeyPort, span.Tag(ext.PeerPort))
 				assert.Equal(t, valkeyPort, span.Tag(ext.TargetPort))
+				assert.Equal(t, 0, span.Tag(ext.ValkeyDatabaseIndex))
+				assert.Equal(t, 0, span.Tag("db.out"))
 				assert.NotNil(t, span)
 				assert.Equal(t, tt.valkeyClientOptions.Username, span.Tag(ext.DBUser))
 				assert.Equal(t, "valkey.command", span.OperationName())