<pre>
bin/
- streak # command executable
- todo # command executable
+ hello # command executable
+ outyet # command executable
pkg/
linux_amd64/
- code.google.com/p/goauth2/
- oauth.a # package object
- github.com/nf/todo/
- task.a # package object
+ github.com/golang/example/
+ stringutil.a # package object
src/
- code.google.com/p/goauth2/
- .hg/ # mercurial repository metadata
- oauth/
- oauth.go # package source
- oauth_test.go # test source
- github.com/nf/
- streak/
- .git/ # git repository metadata
- oauth.go # command source
- streak.go # command source
- todo/
- .git/ # git repository metadata
- task/
- task.go # package source
- todo.go # command source
+ <a href="https://github.com/golang/example/">github.com/golang/example/</a>
+ .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
</pre>
<p>
-This workspace contains three repositories (<code>goauth2</code>,
-<code>streak</code>, and <code>todo</code>) comprising two commands
-(<code>streak</code> and <code>todo</code>) and two libraries
-(<code>oauth</code> and <code>task</code>).
+This workspace contains one repository (<code>example</code>)
+comprising two commands (<code>hello</code> and <code>outyet</code>)
+and one library (<code>stringutil</code>).
+</p>
+
+<p>
+A typical workspace would contain many source repositories containing many
+packages and commands. Most Go programmers keep <i>all</i> their Go source code
+and dependencies in a single workspace.
</p>
<p>
<p>
Again, the first step is to choose a package path (we'll use
-<code>github.com/user/newmath</code>) and create the package directory:
+<code>github.com/user/stringutil</code>) and create the package directory:
</p>
<pre>
-$ <b>mkdir $GOPATH/src/github.com/user/newmath</b>
+$ <b>mkdir $GOPATH/src/github.com/user/stringutil</b>
</pre>
<p>
-Next, create a file named <code>sqrt.go</code> in that directory with the
+Next, create a file named <code>reverse.go</code> in that directory with the
following contents.
</p>
<pre>
-// Package newmath is a trivial example package.
-package newmath
-
-// Sqrt returns an approximation to the square root of x.
-func Sqrt(x float64) float64 {
- z := 1.0
- for i := 0; i < 1000; i++ {
- z -= (z*z - x) / (2 * z)
+// Package stringutil contains utility functions for working with strings.
+package stringutil
+
+// Reverse returns its argument string reversed rune-wise left to right.
+func Reverse(s string) string {
+ r := []rune(s)
+ for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
+ r[i], r[j] = r[j], r[i]
}
- return z
+ return string(r)
}
</pre>
</p>
<pre>
-$ <b>go build github.com/user/newmath</b>
+$ <b>go build github.com/user/stringutil</b>
</pre>
<p>
</p>
<p>
-After confirming that the <code>newmath</code> package builds,
+After confirming that the <code>stringutil</code> package builds,
modify your original <code>hello.go</code> (which is in
<code>$GOPATH/src/github.com/user/hello</code>) to use it:
</p>
import (
"fmt"
- <b>"github.com/user/newmath"</b>
+ <b>"github.com/user/stringutil"</b>
)
func main() {
- fmt.Printf("Hello, world. <b>Sqrt(2) = %v\n", newmath.Sqrt(2)</b>)
+ fmt.Printf(stringutil.Reverse("!oG ,olleH"))
}
</pre>
<p>
Whenever the <code>go</code> tool installs a package or binary, it also
-installs whatever dependencies it has. So when you install the <code>hello</code>
-program
+installs whatever dependencies it has.
+So when you install the <code>hello</code> program
</p>
<pre>
</pre>
<p>
-the <code>newmath</code> package will be installed as well, automatically.
+the <code>stringutil</code> package will be installed as well, automatically.
</p>
<p>
-Running the new version of the program, you should see some numerical output:
+Running the new version of the program, you should see a new, reversed message:
</p>
<pre>
$ <b>hello</b>
-Hello, world. Sqrt(2) = 1.414213562373095
+Hello, Go!
</pre>
<p>
<pre>
bin/
- hello # command executable
+ hello # command executable
pkg/
- linux_amd64/ # this will reflect your OS and architecture
+ linux_amd64/ # this will reflect your OS and architecture
github.com/user/
- newmath.a # package object
+ stringutil.a # package object
src/
github.com/user/
hello/
- hello.go # command source
- newmath/
- sqrt.go # package source
+ hello.go # command source
+ stringutil/
+ reverse.go # package source
</pre>
<p>
-Note that <code>go install</code> placed the <code>newmath.a</code> object in a
-directory inside <code>pkg/linux_amd64</code> that mirrors its source
+Note that <code>go install</code> placed the <code>stringutil.a</code> object
+in a directory inside <code>pkg/linux_amd64</code> that mirrors its source
directory.
This is so that future invocations of the <code>go</code> tool can find the
package object and avoid recompiling the package unnecessarily.
</p>
<p>
-Add a test to the <code>newmath</code> package by creating the file
-<code>$GOPATH/src/github.com/user/newmath/sqrt_test.go</code> containing the
-following Go code.
+Add a test to the <code>stringutil</code> package by creating the file
+<code>$GOPATH/src/github.com/user/stringutil/reverse_test.go</code> containing
+the following Go code.
</p>
<pre>
-package newmath
+package stringutil
import "testing"
-func TestSqrt(t *testing.T) {
- const in, out = 4, 2
- if x := Sqrt(in); x != out {
- t.Errorf("Sqrt(%v) = %v, want %v", in, x, out)
+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)
+ }
}
}
</pre>
</p>
<pre>
-$ <b>go test github.com/user/newmath</b>
-ok github.com/user/newmath 0.165s
+$ <b>go test github.com/user/stringutil</b>
+ok github.com/user/stringutil 0.165s
</pre>
<p>
<pre>
$ <b>go test</b>
-ok github.com/user/newmath 0.165s
+ok github.com/user/stringutil 0.165s
</pre>
<p>
revision control system such as Git or Mercurial. The <code>go</code> tool uses
this property to automatically fetch packages from remote repositories.
For instance, the examples described in this document are also kept in a
-Mercurial repository hosted at Google Code,
-<code><a href="//code.google.com/p/go.example">code.google.com/p/go.example</a></code>.
+Git repository hosted at GitHub
+<code><a href="https://github.com/golang/example">github.com/golang/example</a></code>.
If you include the repository URL in the package's import path,
<code>go get</code> will fetch, build, and install it automatically:
</p>
<pre>
-$ <b>go get code.google.com/p/go.example/hello</b>
+$ <b>go get github.com/golang/example/hello</b>
$ <b>$GOPATH/bin/hello</b>
-Hello, world. Sqrt(2) = 1.414213562373095
+Hello, Go examples!
</pre>
<p>
<pre>
bin/
- hello # command executable
+ hello # command executable
pkg/
linux_amd64/
- code.google.com/p/go.example/
- newmath.a # package object
+ github.com/golang/example/
+ stringutil.a # package object
github.com/user/
- newmath.a # package object
+ stringutil.a # package object
src/
- code.google.com/p/go.example/
+ github.com/golang/example/
+ .git/ # Git repository metadata
hello/
- hello.go # command source
- newmath/
- sqrt.go # package source
- sqrt_test.go # test source
+ hello.go # command source
+ stringutil/
+ reverse.go # package source
+ reverse_test.go # test source
github.com/user/
hello/
- hello.go # command source
- newmath/
- sqrt.go # package source
- sqrt_test.go # test source
+ hello.go # command source
+ stringutil/
+ reverse.go # package source
+ reverse_test.go # test source
</pre>
<p>
-The <code>hello</code> command hosted at Google Code depends on the
-<code>newmath</code> package within the same repository. The imports in
-<code>hello.go</code> file use the same import path convention, so the <code>go
-get</code> command is able to locate and install the dependent package, too.
+The <code>hello</code> command hosted at GitHub depends on the
+<code>stringutil</code> package within the same repository. The imports in
+<code>hello.go</code> file use the same import path convention, so the
+<code>go get</code> command is able to locate and install the dependent
+package, too.
</p>
<pre>
-import "code.google.com/p/go.example/newmath"
+import "github.com/golang/example/stringutil"
</pre>
<p>