diff --git a/go.mod b/go.mod
index 4cf72d1c3..253510833 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/prymitive/karma
 
-go 1.15
+go 1.16
 
 require (
 	github.com/Masterminds/semver/v3 v3.1.1
diff --git a/go.sum b/go.sum
index 9be95b40d..067646d9a 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,6 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/AndreasBriese/bbloom v0.0.0-20190306092124-e2d15f34fcf9/go.mod h1:bOvUY6CB00SOBii9/FifXqc0awNKxLFCL/+pkDPuyl8=
-github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/CloudyKit/fastprinter v0.0.0-20200109182630-33d98a066a53/go.mod h1:+3IMCy2vIlbG1XG/0ggNQv0SvxCAIpPM5b1nCz56Xno=
 github.com/CloudyKit/jet/v3 v3.0.0/go.mod h1:HKQPgSJmdK8hdoAbKUUWajkHyHo4RaU5rMdUywE7VMo=
diff --git a/make/go.mk b/make/go.mk
index 4d35d765a..16f4b4a27 100644
--- a/make/go.mk
+++ b/make/go.mk
@@ -1,7 +1,5 @@
 include make/vars.mk
 
-ENV   := GO111MODULE=on
-GO    := $(ENV) go
 GOBIN := $(shell go env GOBIN)
 ifeq ($(GOBIN),)
 GOBIN = $(shell go env GOPATH)/bin
@@ -11,15 +9,15 @@ ui/build/index.html: $(call rwildcard, ui/src ui/package.json ui/package-lock.js
 	@$(MAKE) -C ui build
 
 $(GOBIN)/go-bindata: tools/go-bindata/go.mod tools/go-bindata/go.sum
-	$(GO) install -modfile=tools/go-bindata/go.mod github.com/go-bindata/go-bindata/...
+	go install -modfile=tools/go-bindata/go.mod github.com/go-bindata/go-bindata/...
 $(GOBIN)/go-bindata-assetfs: $(GOBIN)/go-bindata tools/go-bindata/go.mod tools/go-bindata/go.sum
-	$(GO) install -modfile=tools/go-bindata/go.mod github.com/elazarl/go-bindata-assetfs/...
+	go install -modfile=tools/go-bindata/go.mod github.com/elazarl/go-bindata-assetfs/...
 cmd/karma/bindata_assetfs.go: $(GOBIN)/go-bindata-assetfs $(SOURCES_JS) ui/build/index.html
 	env PATH="$(PATH):$(GOBIN)" $(GOBIN)/go-bindata-assetfs -o cmd/karma/bindata_assetfs.go ui/build/... ui/src/... cmd/karma/tests/bindata/...
 
 .DEFAULT_GOAL := $(NAME)
 $(NAME): go.mod go.sum cmd/karma/bindata_assetfs.go $(SOURCES_GO)
-	$(GO) build -ldflags "-X main.version=$(VERSION)" ./cmd/karma
+	go build -ldflags "-X main.version=$(VERSION)" ./cmd/karma
 
 .PHONY: test-go
 test-go:
@@ -31,27 +29,27 @@ test-go:
 GOBENCHMARKCOUNT := 10
 .PHONY: benchmark-go
 benchmark-go:
-	@env GOMAXPROCS=2 $(GO) test -count=$(GOBENCHMARKCOUNT) -run=NONE -bench=. -benchmem ./...
+	@env GOMAXPROCS=2 go test -count=$(GOBENCHMARKCOUNT) -run=NONE -bench=. -benchmem ./...
 
 $(GOBIN)/benchstat: tools/benchstat/go.mod tools/benchstat/go.sum
-	@$(GO) install -modfile=tools/benchstat/go.mod golang.org/x/perf/cmd/benchstat
+	@go install -modfile=tools/benchstat/go.mod golang.org/x/perf/cmd/benchstat
 benchmark-compare-go: $(GOBIN)/benchstat
 	@$(GOBIN)/benchstat main.txt new.txt
 
 $(GOBIN)/looppointer: tools/looppointer/go.mod tools/looppointer/go.sum
-	$(GO) install -modfile=tools/looppointer/go.mod github.com/kyoh86/looppointer/cmd/looppointer
+	go install -modfile=tools/looppointer/go.mod github.com/kyoh86/looppointer/cmd/looppointer
 .PHONY: lint-go-looppointer
 lint-go-looppointer: $(GOBIN)/looppointer
 	$(ENV) looppointer -c 2 ./...
 
 $(GOBIN)/staticcheck: tools/staticcheck/go.mod tools/staticcheck/go.sum
-	$(GO) install -modfile=tools/staticcheck/go.mod honnef.co/go/tools/cmd/staticcheck
+	go install -modfile=tools/staticcheck/go.mod honnef.co/go/tools/cmd/staticcheck
 .PHONY: lint-go-staticcheck
 lint-go-staticcheck: $(GOBIN)/staticcheck
 	$(ENV) staticcheck ./...
 
 $(GOBIN)/golangci-lint: tools/golangci-lint/go.mod tools/golangci-lint/go.sum
-	$(GO) install -modfile=tools/golangci-lint/go.mod github.com/golangci/golangci-lint/cmd/golangci-lint
+	go install -modfile=tools/golangci-lint/go.mod github.com/golangci/golangci-lint/cmd/golangci-lint
 .PHONY: lint-go
 lint-go: $(GOBIN)/golangci-lint lint-go-looppointer lint-go-staticcheck
 	$(ENV) golangci-lint run -v
@@ -62,8 +60,8 @@ format-go:
 
 .PHONY: download-deps-go
 download-deps-go:
-	@for f in $(wildcard tools/*/go.mod) ; do echo ">>> $$f" && cd $(CURDIR)/`dirname "$$f"` && $(GO) mod download && cd $(CURDIR) ; done
-	$(GO) mod download
+	@for f in $(wildcard tools/*/go.mod) ; do echo ">>> $$f" && cd $(CURDIR)/`dirname "$$f"` && go mod download && cd $(CURDIR) ; done
+	go mod download
 
 .PHONY: install-deps-build-go
 install-deps-build-go: $(GOBIN)/go-bindata-assetfs