upgrade linter

hack/install-linter.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-# Copyright 2022-2025 the Pinniped contributors. All Rights Reserved.
+# Copyright 2022-2026 the Pinniped contributors. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
 
 set -euo pipefail
@@ -13,19 +13,14 @@ go version
 
 lint_version="v$(cat hack/lib/lint-version.txt)"
 
-# Find the toolchain version from our go.mod file. "go install" pays attention to $GOTOOLCHAIN.
-GOTOOLCHAIN=$(sed -rn 's/^toolchain (go[0-9\.]+)$/\1/p' go.mod)
+# Find the Go version from our Dockerfile. "go install" pays attention to $GOTOOLCHAIN.
+GOTOOLCHAIN=$(sed -rn 's/^ARG BUILD_IMAGE=golang:([0-9\.]+)@sha256:.*$/\1/p' Dockerfile)
 if [[ -z "$GOTOOLCHAIN" ]]; then
-  # Did not find toolchain directive. The directive is not needed in a go.mod file when it would be the same
-  # version as the go directive, so it will not always be there. Try using go directive instead.
-  GOTOOLCHAIN=$(sed -rn 's/^go ([0-9]+\.[0-9]+\.[0-9]+)$/\1/p' go.mod)
-  if [[ -z "$GOTOOLCHAIN" ]]; then
-    echo "ERROR: Could not find Go patch version from go.mod file."
-    exit 1
-  fi
-  GOTOOLCHAIN="go${GOTOOLCHAIN}"
+  echo "ERROR: Could not find Go patch version from Dockerfile."
+  exit 1
 fi
 
+GOTOOLCHAIN="go${GOTOOLCHAIN}"
 export GOTOOLCHAIN
 
 echo "Installing golangci-lint@${lint_version} using toolchain ${GOTOOLCHAIN}"

hack/lib/lint-version.txt

@@ -1 +1 @@
-2.7.2
+2.9.0