Add examples

.gitignore

@@ -7,4 +7,5 @@ _obj
 _test
 testdata
 /.idea
-*.iml
+*.iml
+/notes.txt

example_test.go

@@ -0,0 +1,56 @@
+package mmap_test
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/edsrzf/mmap-go"
+)
+
+func ExampleMapRegion() {
+	m, err := mmap.MapRegion(nil, 100, mmap.RDWR, mmap.ANON, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// m acts as a writable slice of bytes that is not managed by the Go runtime.
+	fmt.Println(len(m))
+
+	// Because the region is not managed by the Go runtime, the Unmap method should
+	// be called when finished with it to avoid leaking memory.
+	if err := m.Unmap(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Output: 100
+}
+
+func ExampleMap() {
+	f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0755)
+	if err != nil {
+		log.Fatal(err)
+	}
+	_, err = f.WriteString("Hello, world")
+	if err != nil {
+		log.Fatal(err)
+	}
+	// The file must be closed, even after calling Unmap.
+	defer f.Close()
+
+	m, err := mmap.Map(f, mmap.RDWR, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// m acts as a writable slice of bytes that is a view into the open file, notes.txt.
+	// It is sized to the file contents automatically.
+	fmt.Println(string(m))
+
+	// The Unmap method should be called when finished with it to avoid leaking memory
+	// and to ensure that writes are flushed to disk.
+	if err := m.Unmap(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Hello, world
+}