Merge pull request #4095 from xyz-li/master

go build with vendor by default

Makefile

@@ -15,7 +15,10 @@ GOBIN=$(shell go env GOBIN)
 endif
 
 OUTPUT_DIR=bin
-GOFLAGS=-mod=vendor
+ifeq (${GOFLAGS},)
+	# go build with vendor by default.
+	export GOFLAGS=-mod=vendor
+endif
 define ALL_HELP_INFO
 # Build code.
 #

hack/verify-spelling.sh

@@ -31,6 +31,8 @@ PATH="${GOBIN}:${PATH}"
 
 # Install tools we need
 pushd "${KUBE_ROOT}/hack/tools" >/dev/null
+  # As GOFLAGS may equal to `-mod=vendor`, we must download the modules to vendor or go install will fail.
+  go mod vendor
   GO111MODULE=on go install github.com/client9/misspell/cmd/misspell
 popd >/dev/null