实现一个Golang Module Proxy

//go:generate sh generate.sh
package main

import (
    ...
    "github.com/leileiluoluo/goproxy/pkg/proxy"
)

var port = flag.String("serverPort", ":8080", "server port")

func main() {
    // server
    srv := http.Server{
        Addr:    *port,
        Handler: proxy.Proxy(),
    }

    // server startup / gracefully shutdown
    ...
    srv.ListenAndServe()
    ...
}

#!/bin/bash

mkdir internal

# copy dependencies
cp -r $GOROOT/src/cmd/go/internal/modfetch ./internal/
...
cp -r $GOROOT/src/cmd/internal/sys ./internal/
...

# replace import paths
find . -type f -name "*.go" -exec sed -i '' 's#cmd/go/internal/#github.com/leileiluoluo/goproxy/internal/#g' {} \; 
...

package proxy

import (
    ...
    "github.com/leileiluoluo/goproxy/internal/modfetch"
    ...
)

const (
    ListSuffix   = "/@v/list"
    LatestSuffix = "/@latest"
    InfoSuffix   = ".info"
    ModSuffix    = ".mod"
    ZipSuffix    = ".zip"
    VInfix       = "/@v/"
)

func init() {
    modfetch.PkgMod = ...
    codehost.WorkRoot = ...
}

func Proxy() http.HandlerFunc {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        path := strings.Trim(r.RequestURI, "/")

        // req path validation
        if err := pathValidation(path); nil != err {
            w.WriteHeader(http.StatusBadRequest)
            fmt.Fprintln(w, err)
            return
        }

        switch {
        // suffix is /@v/list
        case strings.HasSuffix(path, ListSuffix):
            ...
            // call modfetch.Lookup(mod)
            lookupVersions(mod)
            ...
            return
        // suffix is /@latest
        case strings.HasSuffix(path, LatestSuffix):
	    ...
            // modfetch.Lookup(mod)
            lookupLatestRev(mod)
            ...
            return
        // suffix is .info
        case strings.HasSuffix(path, InfoSuffix):
            ...
            // call modfetch.Stat(mod, rev)
            loadRev(mod, ver)
            ...
	    return
        // suffix is .mod
        case strings.HasSuffix(path, ModSuffix):
            ...
            // call modfetch.GoMod(mod, rev)
	    loadModContent(mod, ver)
            ...
	    return
        // suffix is .zip
        case strings.HasSuffix(path, ZipSuffix):
            ...
            // call modfetch.DownloadZip(module.Version{Path: mod, Version: rev})
            loadZip(mod, ver)
            ...
	    return
        default:
	    w.WriteHeader(http.StatusBadRequest)
	    fmt.Fprintln(w, "please give me a correct module query")
        }
    })
}