报错情况
下载gin包，报错如下：
unrecognized import path "golang.org/x/crypto/sha3": https fetch: Get "https://golang.org/x/crypto/sha3?go-get=1": dial tcp 216.239.37.1:443: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
unrecognized import path "google.golang.org/protobuf/encoding/prototext": https fetch: Get "https://google.golang.org/protobuf/encoding/prototext?go-get=1": dial tcp 216.239.37.1:443: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
如图：
解决方案
设置代理
cmd下输入：SET GO111MODULE=on
接着cmd输入:SET GOPROXY=https://goproxy.cn
这里参考的文章上是：
在代理链接外添加了双引号，但是事实上：
出现了转义
go get github.com/gin-gonic/gin: parse ""https://goproxy.cn"": first path segment in URL cannot contain colon
所以这里我们灵活修改为 SET GOPROXY=https://goproxy.cn
代理设置完成，成功下载
