diff --git a/.travis.yml b/.travis.yml
index 665a74e87..787a70a08 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ go:
 # add TF_ETCDV3_TEST=1 to run etcdv3 tests
 # if added, TF_ETCDV3_ENDPOINTS must be set to a comma-separated list of (insecure) etcd endpoints against which to test
 env:
-  - CONSUL_VERSION=0.7.5 GOMAXPROCS=4
+  - CONSUL_VERSION=0.7.5 GOMAXPROCS=4 GO111MODULE=on
 
 # Fetch consul for the backend and provider tests
 before_install:
diff --git a/Makefile b/Makefile
index 6c08f8e18..305435d67 100644
--- a/Makefile
+++ b/Makefile
@@ -6,10 +6,10 @@ WEBSITE_REPO=github.com/hashicorp/terraform-website
 default: test
 
 tools:
-	go get -u github.com/kardianos/govendor
-	go get -u golang.org/x/tools/cmd/stringer
-	go get -u golang.org/x/tools/cmd/cover
-	go get -u github.com/golang/mock/mockgen
+	GO111MODULE=off go get -u github.com/kardianos/govendor
+	GO111MODULE=off go get -u golang.org/x/tools/cmd/stringer
+	GO111MODULE=off go get -u golang.org/x/tools/cmd/cover
+	GO111MODULE=off go get -u github.com/golang/mock/mockgen
 
 # bin generates the releaseable binaries for Terraform
 bin: fmtcheck generate
@@ -18,10 +18,10 @@ bin: fmtcheck generate
 # dev creates binaries for testing Terraform locally. These are put
 # into ./bin/ as well as $GOPATH/bin
 dev: fmtcheck generate
-	@TF_DEV=1 sh -c "'$(CURDIR)/scripts/build.sh'"
+	go install -mod=vendor .
 
 quickdev: generate
-	@TF_DEV=1 sh -c "'$(CURDIR)/scripts/build.sh'"
+	go install -mod=vendor .
 
 # Shorthand for building and installing just one plugin for local testing.
 # Run as (for example): make plugin-dev PLUGIN=provider-aws
@@ -33,34 +33,34 @@ plugin-dev: generate
 # we run this one package at a time here because running the entire suite in
 # one command creates memory usage issues when running in Travis-CI.
 test: fmtcheck generate
-	go list $(TEST) | xargs -t -n4 go test $(TESTARGS) -timeout=2m -parallel=4
+	go list -mod=vendor $(TEST) | xargs -t -n4 go test $(TESTARGS) -mod=vendor -timeout=2m -parallel=4
 
 # testacc runs acceptance tests
 testacc: fmtcheck generate
 	@if [ "$(TEST)" = "./..." ]; then \
 		echo "ERROR: Set TEST to a specific package. For example,"; \
-		echo "  make testacc TEST=./builtin/providers/aws"; \
+		echo "  make testacc TEST=./builtin/providers/test"; \
 		exit 1; \
 	fi
-	TF_ACC=1 go test $(TEST) -v $(TESTARGS) -timeout 120m
+	TF_ACC=1 go test $(TEST) -v $(TESTARGS) -mod=vendor -timeout 120m
 
 # e2etest runs the end-to-end tests against a generated Terraform binary
 # The TF_ACC here allows network access, but does not require any special
 # credentials since the e2etests use local-only providers such as "null".
 e2etest: generate
-	TF_ACC=1 go test -v ./command/e2etest
+	TF_ACC=1 go test -mod=vendor -v ./command/e2etest
 
 test-compile: fmtcheck generate
 	@if [ "$(TEST)" = "./..." ]; then \
 		echo "ERROR: Set TEST to a specific package. For example,"; \
-		echo "  make test-compile TEST=./builtin/providers/aws"; \
+		echo "  make test-compile TEST=./builtin/providers/test"; \
 		exit 1; \
 	fi
 	go test -c $(TEST) $(TESTARGS)
 
 # testrace runs the race checker
 testrace: fmtcheck generate
-	TF_ACC= go test -race $(TEST) $(TESTARGS)
+	TF_ACC= go test -mod=vendor -race $(TEST) $(TESTARGS)
 
 cover:
 	@go tool cover 2>/dev/null; if [ $$? -eq 3 ]; then \
@@ -75,10 +75,13 @@ cover:
 # "make protobuf".
 generate:
 	@which stringer > /dev/null; if [ $$? -ne 0 ]; then \
-	  go get -u golang.org/x/tools/cmd/stringer; \
+	  GO111MODULE=off go get -u golang.org/x/tools/cmd/stringer; \
 	fi
-	go generate ./...
-	@go fmt command/internal_plugin_list.go > /dev/null
+	# We turn off modules for "go generate" because our downstream generate
+	# commands are not all ready to deal with Go modules yet, and this
+	# avoids downloading all of the deps that are in the vendor dir anyway.
+	GO111MODULE=off go generate ./...
+	GO111MODULE=off go fmt command/internal_plugin_list.go > /dev/null
 
 # We separate the protobuf generation because most development tasks on
 # Terraform do not involve changing protobuf files and protoc is not a
diff --git a/scripts/build.sh b/scripts/build.sh
index 45e297d1d..bdef1111f 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -47,6 +47,10 @@ if [[ -n "${TF_RELEASE}" ]]; then
     LD_FLAGS="-X main.GitCommit=${GIT_COMMIT}${GIT_DIRTY} -X github.com/hashicorp/terraform/version.Prerelease= -s -w"
 fi
 
+# Ensure all remote modules are downloaded and cached before build so that
+# the concurrent builds launched by gox won't race to redundantly download them.
+go mod download
+
 # Build!
 echo "==> Building..."
 gox \