Merge pull request #562 from GoogleCloudPlatform/dependabot/docker/cu…

…stom-metrics-stackdriver-adapter/golang-1.21-alpine

Bump golang from 1.19-alpine to 1.21-alpine in /custom-metrics-stackdriver-adapter

custom-metrics-stackdriver-adapter/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.19-alpine as builder
+FROM golang:1.21-alpine as builder
 WORKDIR ${GOPATH}/src/github.com/GoogleCloudPlatform/k8s-stackdriver/custom-metrics-stackdriver-adapter
 COPY . ./
 RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -o /adapter