ci(jenkins): retry transient go fetch/test failures

Jenkinsfile

@@ -119,11 +119,36 @@ spec:
             apt-get update >/dev/null
             apt-get install -y --no-install-recommends xz-utils >/dev/null
             mkdir -p build
+            export GOPROXY='https://proxy.golang.org,direct'
+            export GOSUMDB='sum.golang.org'
+            for attempt in 1 2 3; do
+              if go mod download >/dev/null 2>&1; then
+                break
+              fi
+              if [ "${attempt}" -eq 3 ]; then
+                echo "go mod download failed after ${attempt} attempts" >&2
+                break
+              fi
+              sleep $((attempt * 3))
+            done
             go install github.com/jstemmer/go-junit-report/v2@latest
-            set +e
+            test_rc=1
-            go test -v -coverprofile=build/coverage.out ./... > build/test.out 2>&1
+            for attempt in 1 2 3; do
-            test_rc=$?
+              set +e
-            set -e
+              go test -v -count=1 -coverprofile=build/coverage.out ./... > build/test.out 2>&1
+              test_rc=$?
+              set -e
+              if [ "${test_rc}" -eq 0 ]; then
+                break
+              fi
+              if ! grep -q 'TLS handshake timeout' build/test.out 2>/dev/null; then
+                break
+              fi
+              if [ "${attempt}" -eq 3 ]; then
+                break
+              fi
+              sleep $((attempt * 3))
+            done
             printf '%s\n' "${test_rc}" > "${TEST_EXIT_CODE_PATH}"
             cat build/test.out
             "$(go env GOPATH)/bin/go-junit-report" < build/test.out > "${JUNIT_XML}"
@@ -140,10 +165,12 @@ spec:
 
     stage('Publish test metrics') {
       steps {
-        container('publisher') {
+        container('tester') {
           sh '''
             set -eu
-            python scripts/publish_test_metrics.py
+            apt-get update >/dev/null
+            apt-get install -y --no-install-recommends python3 >/dev/null
+            python3 scripts/publish_test_metrics.py
           '''
         }
       }