The new way (Go modules)
A module is a collection of related Go packages that are versioned together as a single unit. Modules record precise dependency requirements and create reproducible builds.
Relationship between repositories, modules and packages:
- A repository contains one (most often) or more Go modules
- Each module contains one or more Go packages
- Each package consists of one or more Go source files in a single directory
# Let's use Go modules for dependency management.
mkdir my-project
cd my-project
go mod init github.com/jreisinger/my-project
# Code away!
vim main.go
You can use go-code to create a Go module skeleton.
See also
- https://golang.org/doc/code.html (official tutorial)
- https://blog.golang.org/using-go-modules
- https://github.com/golang/go/wiki/Modules
The old way (GOPATH, src, …)
Go has a strong opinion about directory structure.
## Set location of your workspace (It's used by the `go` tool)
$ export GOPATH=`pwd`
$ echo $GOPATH
/Users/reisinge/temp/go
A single file program:
## Create a program
$ tree
.
└── src
└── hello # this directory name is the program name
└── main.go # package main
2 directories, 1 file
## Install the program
$ go install hello # compile and install all *.go files in $GOPATH/src/hello
$ tree
.
├── bin
│ └── hello # hello binary that has been built and installed
└── src
└── hello
└── main.go
3 directories, 2 files
## Run the program
$ bin/hello
Hello, world!
A multiple file (and multiple package) program:
## Create a program
$ tree
.
└── src
├── hello
│ └── main.go # package main imports package shuffler
└── shuffler # this directory name is the package name
└── shuffle.go # package shuffler
3 directories, 2 files
## Install the program
$ go install hello # Compile and install all *.go files in
# $GOPATH/src/hello and all *.go files in the
# imported packages.
$ tree
.
├── bin
│ └── hello
├── pkg
│ └── darwin_amd64 # my OS and CPU architecture
│ └── shuffler.a # object file of the imported package
└── src
├── hello
│ └── main.go
└── shuffler
└── shuffle.go
6 directories, 4 files
## Run the program
$ bin/hello
[3 5 1 1 4 9]
The actual source code of the multifile program:
src/hello/main.go
package main
import (
"fmt"
"shuffler"
)
type intSlice []int
func (is intSlice) Len() int {
return len(is)
}
func (is intSlice) Swap(i, j int) {
is[i], is[j] = is[j], is[i]
}
func main() {
i := intSlice{3,1,4,1,5,9}
shuffler.Shuffle(i)
fmt.Println(i)
}
src/shuffler/shuffle.go
package shuffler
import (
"math/rand"
)
type Shuffleable interface {
Len() int
Swap(i, j int)
}
func Shuffle(s Shuffleable) {
for i := 0; i < s.Len(); i++ {
j := rand.Intn(s.Len() - i)
s.Swap(i, j)
}
}