update code

Author: DeyiXu

Dockerfile

@@ -2,6 +2,6 @@ FROM golang:1.13-alpine
 RUN sed -i 's/dl-cdn.alpinelinux.org/mirrors.aliyun.com/g' /etc/apk/repositories
 RUN apk --no-cache add git
 RUN apk --no-cache add gcc
-RUN apk add --no-cache libc-dev
+RUN apk --no-cache add libc-dev
 RUN go env -w GOPROXY=https://goproxy.io,direct
 RUN go env -w GOSUMDB=off