英文:
no required module provides package <imported-package>: go.mod file not found in current directory or any parent directory;
问题
我看到了可能重复的问题，但它们似乎建议使用go模块。但我想知道为什么GOPATH的文档中所述的功能不能直接使用：
> 导入路径P表示在GOPATH环境变量中列出的某个DIR目录下找到的包（更多详细信息请参阅：'go help gopath'）。
我正在尝试从main.go文件中使用root.go
~/src/github.com/himanshugarg/sicp/root$ ls
main.go root.go test.go
root.go文件有包声明：
~/src/github.com/himanshugarg/sicp/root$ head root.go
// 使用牛顿法求平方根
// 基于SICP第30页
package root
import (
"math"
);
func Sqrt(x float64) float64{
goodEnough := func (guess float64) bool {
main.go文件导入了root：
~/src/github.com/himanshugarg/sicp/root$ head main.go
package main
import (
"fmt"
"os"
"strconv"
"github.com/himanshugarg/sicp/root"
);
func main() {
GOPATH已正确设置：
~/src/github.com/himanshugarg/sicp/root$ echo $GOPATH
/home/hgarg
但是构建失败了：
~/src/github.com/himanshugarg/sicp/root$ go build main.go
main.go:7:3: no required module provides package github.com/himanshugarg/sicp/root: go.mod file not found in current directory or any parent directory; see 'go help modules'
我当然可以使用go模块，但我只是想确保GOPATH不再起作用，或者我是否遗漏了什么。
英文:
I have seen possible duplicate questions but they seem to suggest use of go modules. But I was wondering why the well documented functionality of GOPATH doesn't work out of the box:-
> the import path P denotes the package found in the directory DIR/src/P
> for some DIR listed in the GOPATH environment variable (For more
> details see: 'go help gopath').
I am trying to use root.go from the file main.go
~/src/github.com/himanshugarg/sicp/root$ ls
main.go root.go test.go
The file root.go has the package declaration:-
~/src/github.com/himanshugarg/sicp/root$ head root.go
// Find square root using Newton's method
// Based on SICP's on page 30
package root
import (
"math"
);
func Sqrt(x float64) float64{
goodEnough := func (guess float64) bool {
And the file main.go imports root:-
~/src/github.com/himanshugarg/sicp/root$ head main.go
package main
import (
"fmt"
"os"
"strconv"
"github.com/himanshugarg/sicp/root"
);
func main() {
GOPATH is set correctly:-
~/src/github.com/himanshugarg/sicp/root$ echo $GOPATH
/home/hgarg
But the build fails:-
~/src/github.com/himanshugarg/sicp/root$ go build main.go
main.go:7:3: no required module provides package github.com/himanshugarg/sicp/root: go.mod file not found in current directory or any parent directory; see 'go help modules'
Surely I can use go modules but I just want to be sure that GOPATH no longer works or that I am not missing something.
答案1
得分: 2
这是一个已删除评论中发布的链接：https://go.dev/ref/mod#mod-commands，它解释了这个看似破坏(GO)PATH的变化：
大多数go命令可以在模块感知模式(Module-aware mode)或GOPATH模式下运行。在模块感知模式下，go命令使用go.mod文件来查找版本化的依赖项，并且通常从模块缓存中加载包，如果缺少模块，则会下载。在GOPATH模式下，go命令忽略模块；它在vendor目录和GOPATH中查找依赖项。
从Go 1.16开始，默认情况下启用模块感知模式，无论当前目录或任何父目录中是否存在go.mod文件。在较低版本中，只有在当前目录或任何父目录中存在go.mod文件时，才启用模块感知模式。
此外：
可以使用GO111MODULE环境变量来控制模块感知模式，它可以设置为on、off或auto。
如果GO111MODULE=off，go命令将忽略go.mod文件并以GOPATH模式运行。
通过关闭GO111MODULE，我可以按照文档使用GOPATH。
英文:
This link posted in a now deleted comment - https://go.dev/ref/mod#mod-commands - provides an explanation for this seemingly (GO)PATH breaking change:-
> Most go commands may run in Module-aware mode or GOPATH mode. In
> module-aware mode, the go command uses go.mod files to find versioned
> dependencies, and it typically loads packages out of the module cache,
> downloading modules if they are missing. In GOPATH mode, the go
> command ignores modules; it looks in vendor directories and in GOPATH
> to find dependencies.
>
> As of Go 1.16, module-aware mode is enabled by default, regardless of
> whether a go.mod file is present. In lower versions, module-aware mode
> was enabled when a go.mod file was present in the current directory or
> any parent directory.
Further:-
> Module-aware mode may be controlled with the GO111MODULE environment
> variable, which can be set to on, off, or auto.
>
> If GO111MODULE=off, the go command ignores go.mod files and runs in GOPATH mode.
By turning GO111MODULE off I am able to use GOPATH as documented.
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