借“github.com/julienschmidt/httprouter“实践go mod_package can only use path@verydy@latest: can only

背景

执行如下代码，sublime找不到 “github.com/julienschmidt/httprouter”

package main

import (
    "fmt"
    "net/http"
    "log"
    "github.com/julienschmidt/httprouter"
)

func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "Welcome!\n")
}

func Hello(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "hello, %s!\n", ps.ByName("name"))
}

func main() {
    router := httprouter.New()
    router.GET("/", Index)
    router.GET("/hello/:name", Hello)

    log.Fatal(http.ListenAndServe(":8080", router))
}
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解决办法

一、环境变量要对，这几个都要设
set GO111MODULE=on
set GOBIN=E:\go-workspace\bin
set GOPATH=E:\go-workspace
set GOROOT=C:\Program Files\Go

二、
用 go get -u github.com/julienschmidt/httprouter 在E:\go-workspace\pkg\mod下拉取三方库
发现拉下来的是 github.com/julienschmidt/httprouter@v1.3.0
不是 github.com/julienschmidt/httprouter
查看E:\go-workspace\pkg\mod\github.com\julienschmidt\httprouter@v1.3.0下的go mod
发现里面的内容又是
module github.com/julienschmidt/httprouter
go 1.7
对不上啊

自己写的代码import一个带版本后缀的库，发现提示如下错误：
imports github.com/julienschmidt/httprouter@v1.3.0: can only use path@version syntax with ‘go get’ and ‘go install’ in module-aware mode
自己写的代码import一个不带版本后缀的库，发现又提示库找不到，可怕

而且用go mod download github.com/julienschmidt/httprouter@v1.3.0拉，还只能拉有版本后缀的库！！！

解决办法：
将 httprouter@v1.3.0 目录改名叫 httprouter，同时重新 go mod init httprouter 和 go mod tidy
这样就对上了

最后在自己的项目目录下 /e/go-workspace/src/demo1 执行：
go mod init demo1
go mod tidy

再次编译就OK了