display go version in make (#4003)

Makefile

@@ -2,10 +2,13 @@ export PATH := $(GOPATH)/bin:$(PATH)
 export GO111MODULE=on
 LDFLAGS := -s -w
 
-all: fmt build
+all: env fmt build
 
 build: frps frpc
 
+env:
+	@go version
+
 # compile assets into binary file
 file:
 	rm -rf ./assets/frps/static/*