oidc: Remove tailing slash before fetching the provider config.

plugin/pkg/auth/authenticator/token/oidc/oidc.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"strings"
 	"time"
 
 	"github.com/coreos/go-oidc/jose"
@@ -87,7 +88,7 @@ func New(issuerURL, clientID, caFile, usernameClaim string) (*OIDCAuthenticator,
 			return nil, fmt.Errorf("failed to fetch provider config after %v retries", maxRetries)
 		}
 
-		cfg, err = oidc.FetchProviderConfig(hc, issuerURL)
+		cfg, err = oidc.FetchProviderConfig(hc, strings.TrimSuffix(issuerURL, "/"))
 		if err == nil {
 			break
 		}