Update to Go 1.21 (#270)

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

.github/workflows/reusable_monitoring.yml

@@ -65,7 +65,7 @@ jobs:
           ref: "${{ needs.detect-workflow.outputs.ref }}"
       - uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
         with:
-          go-version: '1.20'
+          go-version: '1.21'
       - name: Download artifact
         uses: dawidd6/action-download-artifact@246dbf436b23d7c49e21a7ab8204ca9ecd1fe615 # v2.27.0
         with:

Dockerfile

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.20.7@sha256:bc5f0b5e43282627279fe5262ae275fecb3d2eae3b33977a7fd200c7a760d6f1 as builder
+FROM golang:1.21.1@sha256:970907c870214ecc19784036f9ba93414213473b03c2b0dc1fa90eeb3a563b8f as builder
 ENV APP_ROOT=/opt/app-root
 ENV GOPATH=$APP_ROOT
 
@@ -29,7 +29,7 @@ RUN go build ./cmd/verifier
 RUN CGO_ENABLED=0 go build -gcflags "all=-N -l"  -o verifier_debug ./cmd/verifier
 
 # Multi-Stage build
-FROM golang:1.20.7@sha256:bc5f0b5e43282627279fe5262ae275fecb3d2eae3b33977a7fd200c7a760d6f1 as deploy
+FROM golang:1.21.1@sha256:970907c870214ecc19784036f9ba93414213473b03c2b0dc1fa90eeb3a563b8f as deploy
 
 # Retrieve the binary from the previous stage
 COPY --from=builder /opt/app-root/src/verifier /usr/local/bin/verifier

go.mod

@@ -1,6 +1,6 @@
 module github.com/sigstore/rekor-monitor
 
-go 1.20
+go 1.21
 
 require (
 	github.com/go-openapi/runtime v0.26.0