Merge pull request #1 from kezhenxu94/fix

bugfix: cannot build
diff --git a/Makefile b/Makefile
index 04af575..8e2e68e 100644
--- a/Makefile
+++ b/Makefile
@@ -20,18 +20,13 @@
 FAIL_ON_STDOUT := awk '{ print } END { if (NR > 0) { exit 1 } }'
 
 GO := GO111MODULE=on go
-GO_PATH = $$($(GO) env GOPATH)
+GO_PATH = $(shell $(GO) env GOPATH)
 GO_BUILD = $(GO) build
 GO_GET = $(GO) get
 GO_TEST = $(GO) test
 GO_LINT = $(GO_PATH)/bin/golangci-lint
 GO_LICENSER = $(GO_PATH)/bin/go-licenser
 
-# Ensure GOPATH is set before running build process.
-ifeq "$(GOPATH)" ""
-  $(error Please set the environment variable GOPATH before running `make`)
-endif
-
 all: clean deps lint test build
 
 tools: