如何从Go模块导入特定的包?

Golang 1.11beta2为 Modules .

我无法从go模块导入特定包。

这是生成应用程序时的错误:

$ go install
go: downloading github.com/udhos/modhello/modlib/lib v1.0.0
go: finding github.com/udhos/modhello latest
go: import "github.com/udhos/modhello/modapp" ->
    import "github.com/udhos/modhello/modlib/lib": cannot find module providing package github.com/udhos/modhello/modlib/lib

为什么上面显示的导入失败?

这是模块“modlib”中的包“lib”:

# repo: modhello
# module: modlib
# package: lib
$ cat modhello/modlib/lib/modlib.go
package lib
func Sum(a, b int) int {
    return a + b
}
$ cat modhello/modlib/go.mod
module github.com/udhos/modhello/modlib

这是应用程序“modapp”:

$ cat modhello/modapp/main.go
package main
import (
        "log"
        "github.com/udhos/modhello/modlib/lib"
)
func main() {
        run(1, 2)
}
func run(a, b int) {
        log.Printf("Sum(%d,%d) = %d", a, b, lib.Sum(a, b))
}
$ cat modhello/modapp/go.mod
module github.com/udhos/modhello/modapp
require github.com/udhos/modhello/modlib v1.0.0

git存储库被标记为“modlib/v1.0.0”。这就是发布模块版本的方式。

Go版本:

$ go version
go version go1.11beta2 linux/amd64
$ git --version
git version 2.18.0

我把这个疑问也贴在 golang-nuts : Host two distinct modules in one git repo?