最近在docker中运行了一个ubuntu20的系统，在上面运行golang程序，使用go mod tidy后报错：

tls: failed to verify certificate: x509: certificate signed by unknown authority

如：

go: finding module for package google.golang.org/grpc/credentials/insecure
go: finding module for package github.com/shopspring/decimal
go: finding module for package github.com/stretchr/testify/assert
go: metag_media_server/app imports
	github.com/gin-gonic/gin: module github.com/gin-gonic/gin: Get "https://goproxy.cn/github.com/gin-gonic/gin/@v/list": tls: failed to verify certificate: x509: certificate signed by unknown authority
go: metag_media_server/app/config imports
	github.com/pkg/errors: module github.com/pkg/errors: Get "https://goproxy.cn/github.com/pkg/errors/@v/list": tls: failed to verify certificate: x509: certificate signed by unknown authority
go: metag_media_server/app/config imports
	github.com/spf13/viper: module github.com/spf13/viper: Get "https://goproxy.cn/github.com/spf13/viper/@v/list": tls: failed to verify certificate: x509: certificate signed by unknown authority
go: metag_media_server/app/controller imports
	github.com/axetroy/go-fs: module github.com/axetroy/go-fs: Get "https://goproxy.cn/github.com/axetroy/go-fs/@v/list": tls: failed to verify certificate: x509: certificate signed by unknown authority
go: metag_media_server/app/controller imports

出现这中情况一般都是自己安装全新的ubuntu系统，或者在docker中安装ubuntu镜像，跟我一样。

在网上找了很多资料，都没有解决。

这里提供两种最佳方案：

一：设置http的goproxy

export GOPROXY=http://goproxy.cn
或者
export GOPROXY=http://mirrors.aliyun.com/goproxy/

注意前缀不是https

二：重装ca-certificates

sudo apt-get install --reinstall ca-certificates
sudo apt-get update

之后就可以愉快的使用go mod tidy了