fix: GetAttestationData by double checking the cache

beacon/goclient/attest.go

@@ -48,18 +48,18 @@ func (gc *GoClient) GetAttestationData(slot phase0.Slot, committeeIndex phase0.C
 	spec.DataVersion,
 	error,
 ) {
-	// Check cache.
-	cachedResult := gc.attestationDataCache.Get(slot)
-	if cachedResult != nil {
-		data, err := withCommitteeIndex(cachedResult.Value(), committeeIndex)
-		if err != nil {
-			return nil, DataVersionNil, fmt.Errorf("failed to set committee index: %w", err)
-		}
-		return data, spec.DataVersionPhase0, nil
-	}
-
 	// Have to make beacon node request and cache the result.
 	result, err, _ := gc.attestationReqInflight.Do(slot, func() (*phase0.AttestationData, error) {
+		// Check cache.
+		cachedResult := gc.attestationDataCache.Get(slot)
+		if cachedResult != nil {
+			data, err := withCommitteeIndex(cachedResult.Value(), committeeIndex)
+			if err != nil {
+				return nil, fmt.Errorf("failed to set committee index: %w", err)
+			}
+			return data, nil
+		}
+
 		attDataReqStart := time.Now()
 		resp, err := gc.multiClient.AttestationData(gc.ctx, &api.AttestationDataOpts{
 			Slot: slot,