pipe character support problems

[ZhangYunHao]

Look like we have not implemented this feature correctly. For example
g.GoBinEnv = append(os.Environ(), "GOPROXY=http://baidu.com|https://goproxy.io")
and curl this link
http://0.0.0.0:8080/github.com/google/go-dap/@v/v0.2.0.mod
we can got an error
github.com/google/go-dap@v0.2.0: malformed record data

The reason is that we skip errors in sumdb_client_ops.go:(sco *sumdbClientOps) load(), this function only called at initialization, but this error occurred in goproxy.go:zipLines, err := g.sumdbClient.Lookup, which called during fetching. Maybe we should skip errors after g.sumdbClient.Lookup?

Go1.15 implements this feature in https://github.com/golang/go/blob/release-branch.go1.15/src/cmd/go/internal/modfetch/proxy.go#L196 may have some help.

[Aofei Sheng]

Sorry, I don’t think this is our problem, but Baidu's. They returned 200 OK for all error responses, which is totally wrong.

Try this:

$ curl -LI https://baidu.com/sumdb/sum.golang.org/supported

According this, we need to treat 200 OK as the expected response. So.

[ZhangYunHao]

Sure. Baidu in the wrong way, after reading some doc like: https://go.googlesource.com/proposal/+/master/design/25530-sumdb.md#proxying-a-checksum-database , looks like the pipe feature in GOPROXY doesn't provides a fallback for those proxies support checksum database.

Let's makes a simple fake server, which return 200 response in sumdb/sum.golang.org/supported but return 404 response for others.

fake server:
`package main

import (
"github.com/gin-gonic/gin"
)

func main() {
r := gin.Default()
r.GET("/sumdb/sum.golang.org/supported", func(c *gin.Context) {
c.Data(200, "text/plain", []byte("ok"))
})
r.Run("0.0.0.0:7070")
}`

Go 1.15 env

go env -w GOPROXY="http://{MY_IP}:7070|http://goproxy.cn"

It can also got an error. Anyway, for now the proxy is consistent with the behavior of Go1.15. Thanks for your quick reply!