chore: Update Copyright (#1981)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

.golangci.yaml

@@ -29,6 +29,27 @@ linters:
           msg: use golang.org/x/sys/windows instead of syscall
         - pattern: ^windows\.NewLazyDLL$
           msg: use NewLazySystemDLL instead NewLazyDLL
+    goheader:
+      values:
+        const:
+          COMPANY: The Prometheus Authors
+      template: |-
+        SPDX-License-Identifier: Apache-2.0
+
+        Copyright {{ YEAR }} {{ COMPANY }}
+        Licensed under the Apache License, Version 2.0 (the "License");
+        you may not use this file except in compliance with the License.
+        You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+        Unless required by applicable law or agreed to in writing, software
+        distributed under the License is distributed on an "AS IS" BASIS,
+        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+        See the License for the specific language governing permissions and
+        limitations under the License.
+    gomoddirectives:
+      toolchain-forbidden: true
     gosec:
       excludes:
         - G101