ci(metis): retry go downloads and always emit test outputs

Jenkinsfile

@@ -188,7 +188,26 @@ PY
             apt-get update >/dev/null
             apt-get install -y --no-install-recommends xz-utils >/dev/null
             mkdir -p build
-            go install github.com/jstemmer/go-junit-report/v2@latest
+            run_with_retry() {
+              attempts="$1"
+              shift
+              try=1
+              delay=3
+              while true; do
+                "$@" && return 0
+                rc=$?
+                if [ "${try}" -ge "${attempts}" ]; then
+                  return "${rc}"
+                fi
+                echo "[quality] retry ${try}/${attempts} after rc=${rc}: $*" >&2
+                sleep "${delay}"
+                delay=$((delay * 2))
+                try=$((try + 1))
+              done
+            }
+            export GOPROXY="${GOPROXY:-https://proxy.golang.org,direct}"
+            run_with_retry 3 go install github.com/jstemmer/go-junit-report/v2@latest
+            run_with_retry 4 go mod download
             docs_rc=1
             quality_rc=1
             test_rc=1
@@ -205,7 +224,10 @@ PY
             cd "${WORKSPACE}"
 
             if [ "${docs_rc}" -eq 0 ] && [ "${quality_rc}" -eq 0 ]; then
-              go test -v -count=1 -coverprofile=build/coverage.out ./... > build/test.out 2>&1
+              run_with_retry 3 go test -v -count=1 -coverprofile=build/coverage.out ./... > build/test.out 2>&1
+              test_rc=$?
+            else
+              run_with_retry 3 go test -v -count=1 -coverprofile=build/coverage.out ./... > build/test.out 2>&1
               test_rc=$?
             fi
             set -e