Add example package and test

The test-merging section was failing due to the lack of a test
and thus lack of coverage files. This introduces a basic example test
project so that this can be demonstrated.

go.mod

@@ -1,3 +1,5 @@
 module github.com/friendly-fhir/go-template
 
 go 1.22.3
+
+require github.com/google/go-cmp v0.6.0

go.sum

@@ -0,0 +1,2 @@
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=

internal/greeting/greeting.go

@@ -0,0 +1,5 @@
+package greeting
+
+func New() string {
+	return "Hello, world!"
+}

internal/greeting/greeting_test.go

@@ -0,0 +1,18 @@
+package greeting_test
+
+import (
+	"testing"
+
+	"github.com/friendly-fhir/go-template/internal/greeting"
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestNew(t *testing.T) {
+	want := "Hello, world!"
+
+	got := greeting.New()
+
+	if !cmp.Equal(got, want) {
+		t.Errorf("greeting.New() = %q, want %q", got, want)
+	}
+}

main.go

@@ -1,7 +1,11 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+
+	"github.com/friendly-fhir/go-template/internal/greeting"
+)
 
 func main() {
-	fmt.Println("Hello, World!")
+	fmt.Println(greeting.New())
 }