use aliyun mirror when build

README.md

@@ -15,7 +15,10 @@ Nightingale user manual: [https://n9e.didiyun.com/](https://n9e.didiyun.com/)
 mkdir -p $GOPATH/src/github.com/didi
 cd $GOPATH/src/github.com/didi
 git clone https://github.com/didi/nightingale.git
-cd nightingale && ./control build
+cd nightingale
+# export env[GOPROXY] if your network is not good
+# export GOPROXY=https://mirrors.aliyun.com/goproxy/
+./control build
 ```
 
 ## Team

README_ZH.md

@@ -15,7 +15,10 @@ Nightingale是一套衍生自Open-Falcon的互联网监控解决方案，融入
 mkdir -p $GOPATH/src/github.com/didi
 cd $GOPATH/src/github.com/didi
 git clone https://github.com/didi/nightingale.git
-cd nightingale && ./control build
+cd nightingale
+# 如果网络环境不好可以尝试aliyun的mirror
+# export GOPROXY=https://mirrors.aliyun.com/goproxy/
+./control build
 ```
 
 ## 团队

control

@@ -142,7 +142,6 @@ build_one()
 build()
 {
   export GO111MODULE=on
-  export GOPROXY=https://mirrors.aliyun.com/goproxy/
 
 	mod=$1
 	if [ "x${mod}" = "x" ]; then