Overview

  • Go programmers typically keep all their Go code in a single workspace.
  • A workspace contains many version control repositories (managed by Git, for example).
  • Each repository contains one or more packages.
  • Each package consists of one or more Go source files in a single directory.
  • The path to a package’s directory determines its import path.

Note that this differs from other programming environments in which every project has a separate workspace and workspaces are closely tied to version control repositories.

Code organization

Workspaces

A workspace is a directory hierarchy with three directories at its root:

  • src contains Go source files,
  • pkg contains package objects, and
  • bin contains executable commands.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
bin/
    hello                          # command executable
    outyet                         # command executable
pkg/
    linux_amd64/
        github.com/golang/example/
            stringutil.a           # package object
src/
    github.com/golang/example/
        .git/                      # Git repository metadata
	hello/
	    hello.go               # command source
	outyet/
	    main.go                # command source
	    main_test.go           # test source
	stringutil/
	    reverse.go             # package source
	    reverse_test.go        # test source
    golang.org/x/image/
        .git/                      # Git repository metadata
	bmp/
	    reader.go              # package source
	    writer.go              # package source
    ... (many more repositories and packages omitted) ...

The GOPATH environment variable

The GOPATH environment variable specifies the location of your workspace. It defaults to a directory named go inside your home directory, so $HOME/go on Unix, $home/go on Plan 9, and %USERPROFILE%\go (usually C:\Users\YourName\go) on Windows.

For convenience, add the workspace’s bin subdirectory to your PATH:

1
$ export PATH=$PATH:$(go env GOPATH)/bin

The scripts in the rest of this document use $GOPATH instead of $(go env GOPATH) for brevity. To make the scripts run as written if you have not set GOPATH, you can substitute $HOME/go in those commands or else run:

1
$ export GOPATH=$(go env GOPATH)

Import paths

An import path is a string that uniquely identifies a package. A package’s import path corresponds to its location inside a workspace or in a remote repository (explained below).

The packages from the standard library are given short import paths such as “fmt” and “net/http”. For your own packages, you must choose a base path that is unlikely to collide with future additions to the standard library or other external libraries.

Your first program

1
2
3
4
5
6
7
package main

import "fmt"

func main() {
	fmt.Printf("Hello, world.\n")
}
1
go install github.com/user/hello

You can now run the program by typing its full path at the command line:

1
2
$ $GOPATH/bin/hello
Hello, world.

Or, as you have added $GOPATH/bin to your PATH, just type the binary name:

1
2
$ hello
Hello, world.

Package names

The first statement in a Go source file must be

1
package name

Testing

Go has a lightweight test framework composed of the go test command and the testing package.

You write a test by creating a file with a name ending in _test.go that contains functions named TestXXX with signature func (t *testing.T). The test framework runs each such function; if the function calls a failure function such as t.Error or t.Fail, the test is considered to have failed.

Add a test to the stringutil package by creating the file $GOPATH/src/github.com/user/stringutil/reverse_test.go containing the following Go code.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
package stringutil

import "testing"

func TestReverse(t *testing.T) {
	cases := []struct {
		in, want string
	}{
		{"Hello, world", "dlrow ,olleH"},
		{"Hello, 世界", "界世 ,olleH"},
		{"", ""},
	}
	for _, c := range cases {
		got := Reverse(c.in)
		if got != c.want {
			t.Errorf("Reverse(%q) == %q, want %q", c.in, got, c.want)
		}
	}
}

Then run the test with go test:

1
2
$ go test github.com/user/stringutil
ok  	github.com/user/stringutil 0.165s

As always, if you are running the go tool from the package directory, you can omit the package path:

1
2
$ go test
ok  	github.com/user/stringutil 0.165s

Remote packages

1
2
3
$ go get github.com/golang/example/hello
$ $GOPATH/bin/hello
Hello, Go examples!
1
import "github.com/golang/example/stringutil"

Reference

转载请注明来源,https://blog.vicyu.com
由于水平有限，行文难免出错，恳请读者批评指正。