fix: Calling err.Error() on nil error causes panic (#579)

Signed-off-by: Daniel Graña <dangra@gmail.com>
Co-authored-by: Thomas Poignant <thomas.poignant@gofeatureflag.org>

providers/go-feature-flag/pkg/controller/goff_api.go

@@ -4,10 +4,11 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"github.com/open-feature/go-sdk-contrib/providers/go-feature-flag/pkg/model"
 	"net/http"
 	"net/url"
 	"path"
+
+	"github.com/open-feature/go-sdk-contrib/providers/go-feature-flag/pkg/model"
 )
 
 type GoFeatureFlagApiOptions struct {
@@ -104,7 +105,7 @@ func (g *GoFeatureFlagAPI) ConfigurationHasChanged() (ConfigurationChangeStatus,
 	case http.StatusNotModified:
 		return FlagConfigurationNotChanged, nil
 	default:
-		return ErrorConfigurationChange, err
+		return ErrorConfigurationChange, fmt.Errorf("request failed with status: %v", response.Status)
 	}
 }
 

providers/go-feature-flag/pkg/provider.go

@@ -3,12 +3,13 @@ package gofeatureflag
 import (
 	"context"
 	"fmt"
+	"time"
+
 	"github.com/open-feature/go-sdk-contrib/providers/go-feature-flag/pkg/controller"
 	"github.com/open-feature/go-sdk-contrib/providers/go-feature-flag/pkg/hook"
 	"github.com/open-feature/go-sdk-contrib/providers/go-feature-flag/pkg/util"
 	"github.com/open-feature/go-sdk-contrib/providers/ofrep"
 	of "github.com/open-feature/go-sdk/openfeature"
-	"time"
 )
 
 const providerName = "GO Feature Flag"
@@ -245,7 +246,8 @@ func (p *Provider) startPolling(pollingInterval time.Duration) {
 					p.events <- of.Event{
 						ProviderName: providerName, EventType: of.ProviderStale,
 						ProviderEventDetails: of.ProviderEventDetails{
-							Message: "Impossible to check configuration change " + err.Error()},
+							Message: fmt.Sprintf("Impossible to check configuration change: %s", err),
+						},
 					}
 				}
 			}