详解golang中 work与 module 的区别与联系

 module example.com/hello
 ​
 go 1.20
 ​
 replace example.com/greetings => ../greetings
 ​
 require example.com/greetings v0.0.0-00010101000000-000000000000

 ❯ go version
 go version go1.20.7 darwin/amd64

 ❯ go help work
 Work provides access to operations on workspaces.
 ​
 Note that support for workspaces is built into many other commands, not
 just 'go work'.
 ​
 See 'go help modules' for information about Go's module system of which
 workspaces are a part.
 ​
 See https://go.dev/ref/mod#workspaces for an in-depth reference on
 workspaces.
 ​
 See https://go.dev/doc/tutorial/workspaces for an introductory
 tutorial on workspaces.
 ​
 A workspace is specified by a go.work file that specifies a set of
 module directories with the "use" directive. These modules are used as
 root modules by the go command for builds and related operations.  A
 workspace that does not specify modules to be used cannot be used to do
 builds from local modules.
 ​
 go.work files are line-oriented. Each line holds a single directive,
 made up of a keyword followed by arguments. For example:
 ​
   go 1.18
 ​
   use ../foo/bar
   use ./baz
 ​
   replace example.com/foo v1.2.3 => example.com/bar v1.4.5
 ​
 The leading keyword can be factored out of adjacent lines to create a block,
 like in Go imports.
 ​
   use (
     ../foo/bar
     ./baz
   )
 ​
 The use directive specifies a module to be included in the workspace's
 set of main modules. The argument to the use directive is the directory
 containing the module's go.mod file.
 ​
 The go directive specifies the version of Go the file was written at. It
 is possible there may be future changes in the semantics of workspaces
 that could be controlled by this version, but for now the version
 specified has no effect.
 ​
 The replace directive has the same syntax as the replace directive in a
 go.mod file and takes precedence over replaces in go.mod files.  It is
 primarily intended to override conflicting replaces in different workspace
 modules.
 ​
 To determine whether the go command is operating in workspace mode, use
 the "go env GOWORK" command. This will specify the workspace file being
 used.
 ​
 Usage:
 ​
   go work <command> [arguments]
 ​
 The commands are:
 ​
   edit        edit go.work from tools or scripts
   init        initialize workspace file
   sync        sync workspace build list to modules
   use         add modules to workspace file
 ​
 Use "go help work <command>" for more information about a command.

 ❯ tree
 ├── example
 └── mypkg

 ❯ go mod init github.com/example
 go: /Users/oo7/Developer/works/example/go.mod already exists

 ❯ go mod init github.com/mypkg
 go: /Users/oo7/Developer/works/mypkg/go.mod already exists

 package mypkg
 ​
 func Bar() {
   println("this package is mypkg")
 }

 package main
 ​
 import (
   "github.com/mypkg"
 )
 ​
 func main() {
   mypkg.Bar()
 }

 ❯ cd example/
 ❯ go mod tidy
 go: finding module for package github.com/mypkg
 github.com/example imports
         github.com/mypkg: cannot find module providing package github.com/mypkg: invalid github.com import path "github.com/mypkg"
 ❯ cd ../mypkg/
 ❯ go mod tidy
 ~/Developer/works/mypkg ❯    

 ❯ cd example/
 ❯ go run .
 main.go:4:2: no required module provides package github.com/mypkg; to add it:
         go get github.com/mypkg

 ❯ go work init example mypkg
 go: /Users/oo7/Developer/works/go.work already exists

 go 1.20
 ​
 use (
   ./example
   ./mypkg
 )

 ❯ go run .
 this package is mypkg

 ❯ GOWORK=off go run main.go
 main.go:4:2: no required module provides package github.com/mypkg; to add it:
         go get github.com/mypkg