diff --git a/test b/test
index 82c17118c..1cf4c247a 100755
--- a/test
+++ b/test
@@ -33,6 +33,11 @@
 # $ COVERDIR=coverage PASSES="build_cov cov" ./test
 set -e
 
+# The test script is not supposed to make any changes to the files
+# e.g. add/update missing dependencies. Such divergences should be 
+# detected and trigger a failure that needs explicit developer's action.
+export GOFLAGS=-mod=readonly
+
 source ./build
 
 # build before setting up test GOPATH
@@ -152,7 +157,7 @@ function unit_pass {
 	else
 		USERTIMEOUT="${TIMEOUT}"
 	fi
-	go test -mod=mod ${GO_TEST_FLAG} -timeout "${USERTIMEOUT}"  "${COVER}" ${RACE} -cpu "${TEST_CPUS}" ${RUN_ARG} "$@" "${TEST[@]}"
+	go test ${GO_TEST_FLAG} -timeout "${USERTIMEOUT}"  "${COVER}" ${RACE} -cpu "${TEST_CPUS}" ${RUN_ARG} "$@" "${TEST[@]}"
 }
 
 function integration_pass {
@@ -172,7 +177,7 @@ function integration_pass {
 	# if TESTCASE not set, PKG set, run all test cases in specified package
 	# if TESTCASE not set, PKG not set, run all tests in all integration and integration_extra packages
 	if [ -z "${TESTCASE}" ] && [ -z "${USERPKG}" ]; then
-		go test -mod=mod -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration"
+		go test -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration"
 		integration_extra "$@"
 	else
 		if [ -z "${USERPKG}" ]; then
@@ -183,16 +188,16 @@ function integration_pass {
 		else
 			INTEGTESTPKG=("${TEST[@]}")
 		fi
-		go test -mod=mod -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "${RUN_ARG}"  "$@" "${INTEGTESTPKG[@]}"
+		go test -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "${RUN_ARG}"  "$@" "${INTEGTESTPKG[@]}"
 	fi
 }
 
 function integration_extra {
-	go test -mod=mod -timeout 1m -v ${RACE} -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/client/integration"
-	go test -mod=mod -timeout 25m -v ${RACE} -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/clientv3/integration"
-	go test -mod=mod -timeout 1m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/contrib/raftexample"
-	go test -mod=mod -timeout 5m -v ${RACE} -tags v2v3 "$@" "${REPO_PATH}/etcdserver/api/v2store"
-	go test -mod=mod -timeout 1m -v ${RACE} -cpu "${TEST_CPUS}" -run=Example "$@" "${TEST[@]}"
+	go test -timeout 1m -v ${RACE} -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/client/integration"
+	go test -timeout 25m -v ${RACE} -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/clientv3/integration"
+	go test -timeout 1m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/contrib/raftexample"
+	go test -timeout 5m -v ${RACE} -tags v2v3 "$@" "${REPO_PATH}/etcdserver/api/v2store"
+	go test -timeout 1m -v ${RACE} -cpu "${TEST_CPUS}" -run=Example "$@" "${TEST[@]}"
 }
 
 function functional_pass {
@@ -269,26 +274,26 @@ function cov_pass {
 	for t in $(echo "${TEST_PKGS}" | grep -vE "(tests/e2e|functional)"); do
 		tf=$(echo "$t" | tr / _)
 		# cache package compilation data for faster repeated builds
-		go test -mod=mod "${GOCOVFLAGS[@]}" -i "${REPO_PATH}/$t" || true
+		go test "${GOCOVFLAGS[@]}" -i "${REPO_PATH}/$t" || true
 		# uses -run=Test to skip examples because clientv3/ example tests will leak goroutines
-		go test -mod=mod "${GOCOVFLAGS[@]}" -run=Test -coverprofile "$COVERDIR/${tf}.coverprofile"  "${REPO_PATH}/$t" || failed="$failed $t"
+		go test "${GOCOVFLAGS[@]}" -run=Test -coverprofile "$COVERDIR/${tf}.coverprofile"  "${REPO_PATH}/$t" || failed="$failed $t"
 	done
 
 	# v2v3 tests
-	go test -mod=mod -tags v2v3 "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/store-v2v3.coverprofile" "${REPO_PATH}/clientv3/integration" || failed="$failed store-v2v3"
+	go test -tags v2v3 "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/store-v2v3.coverprofile" "${REPO_PATH}/clientv3/integration" || failed="$failed store-v2v3"
 
 	# proxy tests
-	go test -mod=mod -tags cluster_proxy "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/proxy_integration.coverprofile" "${REPO_PATH}/integration" || failed="$failed proxy-integration"
-	go test -mod=mod -tags cluster_proxy "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/proxy_clientv3.coverprofile" "${REPO_PATH}/clientv3/integration" || failed="$failed proxy-clientv3/integration"
+	go test -tags cluster_proxy "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/proxy_integration.coverprofile" "${REPO_PATH}/integration" || failed="$failed proxy-integration"
+	go test -tags cluster_proxy "${GOCOVFLAGS[@]}" -coverprofile "$COVERDIR/proxy_clientv3.coverprofile" "${REPO_PATH}/clientv3/integration" || failed="$failed proxy-clientv3/integration"
 
 	# run code coverage for e2e tests
 	# use 30m timeout because e2e coverage takes longer
 	# due to many tests cause etcd process to wait
 	# on leadership transfer timeout during gracefully shutdown
 	echo Testing tests/e2e without proxy...
-	go test -mod=mod -tags cov -timeout 30m -v "${REPO_PATH}/tests/e2e" || failed="$failed tests/e2e"
+	go test -tags cov -timeout 30m -v "${REPO_PATH}/tests/e2e" || failed="$failed tests/e2e"
 	echo Testing tests/e2e with proxy...
-	go test -mod=mod -tags "cov cluster_proxy" -timeout 30m -v "${REPO_PATH}/tests/e2e" || failed="$failed tests/e2e-proxy"
+	go test -tags "cov cluster_proxy" -timeout 30m -v "${REPO_PATH}/tests/e2e" || failed="$failed tests/e2e-proxy"
 
 	# incrementally merge to get coverage data even if some coverage files are corrupted
 	# optimistically assume etcdserver package's coverage file is OK since gocovmerge
@@ -328,15 +333,15 @@ function e2e_pass {
 		USERTIMEOUT="${TIMEOUT}"
 	fi
 
-	go test -mod=mod -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "${RUN_ARG}"  "$@" "${REPO_PATH}/tests/e2e"
+	go test -timeout "${USERTIMEOUT}" -v -cpu "${TEST_CPUS}" "${RUN_ARG}"  "$@" "${REPO_PATH}/tests/e2e"
 }
 
 function integration_e2e_pass {
 	echo "Running integration and e2e tests..."
 
-	go test -mod=mod -timeout 30m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/tests/e2e" &
+	go test -timeout 30m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/tests/e2e" &
 	e2epid="$!"
-	go test -mod=mod -timeout 30m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration" &
+	go test -timeout 30m -v -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration" &
 	intpid="$!"
 	wait $e2epid
 	wait $intpid
@@ -344,9 +349,9 @@ function integration_e2e_pass {
 }
 
 function grpcproxy_pass {
-	go test -mod=mod -timeout 30m -v ${RACE} -tags cluster_proxy -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration"
-	go test -mod=mod -timeout 30m -v ${RACE} -tags cluster_proxy -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/clientv3/integration"
-	go test -mod=mod -timeout 30m -v -tags cluster_proxy "$@" "${REPO_PATH}/tests/e2e"
+	go test -timeout 30m -v ${RACE} -tags cluster_proxy -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/integration"
+	go test -timeout 30m -v ${RACE} -tags cluster_proxy -cpu "${TEST_CPUS}" "$@" "${REPO_PATH}/clientv3/integration"
+	go test -timeout 30m -v -tags cluster_proxy "$@" "${REPO_PATH}/tests/e2e"
 }
 
 function release_pass {
@@ -450,7 +455,7 @@ function gofmt_pass {
 }
 
 function govet_pass {
-	vetRes=$(go vet -mod=mod "${TEST[@]}")
+	vetRes=$(go vet "${TEST[@]}")
 	if [ -n "${vetRes}" ]; then
 		echo -e "govet checking failed:\\n${vetRes}"
 		exit 255
@@ -641,7 +646,7 @@ function bom_pass {
 	fi
 	echo "Checking bill of materials..."
 	# https://github.com/golang/go/commit/7c388cc89c76bc7167287fb488afcaf5a4aa12bf
-	GOFLAGS="-mod=mod" license-bill-of-materials \
+	license-bill-of-materials \
 		--override-file bill-of-materials.override.json \
 		go.etcd.io/etcd/v3 go.etcd.io/etcd/v3/etcdctl >bom-now.json || true
 	if ! diff bill-of-materials.json bom-now.json; then
@@ -667,16 +672,16 @@ function dep_pass {
 function build_cov_pass {
 	out="bin"
 	if [ -n "${BINDIR}" ]; then out="${BINDIR}"; fi
-	go test -mod=mod -tags cov -c -covermode=set -coverpkg="$PKGS_COMMA" -o "${out}/etcd_test"
+	go test -tags cov -c -covermode=set -coverpkg="$PKGS_COMMA" -o "${out}/etcd_test"
 
-	go test -mod=mod -tags cov -c -covermode=set -coverpkg="$PKGS_COMMA" -o "${out}/etcdctl_test" "${REPO_PATH}/etcdctl"
+	go test -tags cov -c -covermode=set -coverpkg="$PKGS_COMMA" -o "${out}/etcdctl_test" "${REPO_PATH}/etcdctl"
 }
 
 # fail fast on static tests
 function build_pass {
 	echo "Checking build..."
-	GO_BUILD_FLAGS="-v -mod=mod" etcd_build
-	GO_BUILD_FLAGS="-v -mod=mod" tools_build
+	GO_BUILD_FLAGS="-v" etcd_build
+	GO_BUILD_FLAGS="-v" tools_build
 }
 
 for pass in $PASSES; do