Add a Go language example.

This follows the other examples so that it can be used as a tutorial,
such as the ones at:
  https://developers.google.com/protocol-buffers/docs/tutorials

Even though Go generally does not use Makefiles, I added targets for the
Go examples to be consistent with the other languages.

Edit:

Fix Travis run. Change to use $HOME instead of ~. Add protoc to path.
GOPATH entry cannot start with shell metacharacter '~': "~/gocode"

Edit(2):

Fix Go code style to address comments.

1 files changed, 96 insertions, 0 deletions

diff --git a/examples/list_people_test.go b/examples/list_people_test.go
new file mode 100644
index 00000000..721d3555
--- /dev/null
+++ b/examples/list_people_test.go
@@ -0,0 +1,96 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	pb "github.com/google/protobuf/examples/tutorial"
+)
+
+func TestListPeopleWritesList(t *testing.T) {
+	buf := new(bytes.Buffer)
+	in := pb.AddressBook{[]*pb.Person{
+		{
+			Name:  "John Doe",
+			Id:    101,
+			Email: "john@example.com",
+		},
+		{
+			Name: "Jane Doe",
+			Id:   102,
+		},
+		{
+			Name:  "Jack Doe",
+			Id:    201,
+			Email: "jack@example.com",
+			Phones: []*pb.Person_PhoneNumber{
+				{Number: "555-555-5555", Type: pb.Person_WORK},
+			},
+		},
+		{
+			Name:  "Jack Buck",
+			Id:    301,
+			Email: "buck@example.com",
+			Phones: []*pb.Person_PhoneNumber{
+				{Number: "555-555-0000", Type: pb.Person_HOME},
+				{Number: "555-555-0001", Type: pb.Person_MOBILE},
+				{Number: "555-555-0002", Type: pb.Person_WORK},
+			},
+		},
+		{
+			Name:  "Janet Doe",
+			Id:    1001,
+			Email: "janet@example.com",
+			Phones: []*pb.Person_PhoneNumber{
+				{Number: "555-777-0000"},
+				{Number: "555-777-0001", Type: pb.Person_HOME},
+			},
+		},
+	}}
+	listPeople(buf, &in)
+	want := strings.Split(`Person ID: 101
+  Name: John Doe
+  E-mail address: john@example.com
+Person ID: 102
+  Name: Jane Doe
+Person ID: 201
+  Name: Jack Doe
+  E-mail address: jack@example.com
+  Work phone #: 555-555-5555
+Person ID: 301
+  Name: Jack Buck
+  E-mail address: buck@example.com
+  Home phone #: 555-555-0000
+  Mobile phone #: 555-555-0001
+  Work phone #: 555-555-0002
+Person ID: 1001
+  Name: Janet Doe
+  E-mail address: janet@example.com
+  Mobile phone #: 555-777-0000
+  Home phone #: 555-777-0001
+`, "\n")
+	got := strings.Split(buf.String(), "\n")
+	if len(got) != len(want) {
+		t.Errorf(
+			"listPeople(%s) =>\n\t%q has %d lines, want %d",
+			in.String(),
+			buf.String(),
+			len(got),
+			len(want))
+	}
+	lines := len(got)
+	if lines > len(want) {
+		lines = len(want)
+	}
+	for i := 0; i < lines; i++ {
+		if got[i] != want[i] {
+			t.Errorf(
+				"listPeople(%s) =>\n\tline %d %q, want %q",
+				in.String(),
+				i,
+				got[i],
+				want[i])
+		}
+	}
+}