feat: add CopyOnWriteList. A thread-safe list. (#125)

* fix: use loop to get value . On Get() and Contains()

* fix: Use reflect. DeepEqual() determines whether the keys are equal

* feat: add CopyOnWriteList. A thread-safe list.

* fix: fix failed unit test

* feat: add Equal() in CopyOnWriteList.

fix: update some function`s  names

* doc: add copyonwritelist.md and copyonwritelist_zh-CN.md

datastructure/hashmap/hashmap_test.go

@@ -74,3 +74,34 @@ func TestHashMap_KeysValues(t *testing.T) {
 	assert.Equal(3, len(values))
 	assert.Equal(3, len(keys))
 }
+
+func TestHashMap_Keys(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestHashMap_Keys")
+
+	hm := NewHashMap()
+
+	hm.Put("a", 1)
+	hm.Put("b", 2)
+	hm.Put("c", 3)
+
+	keys := hm.Keys()
+
+	assert.Equal(3, len(keys))
+}
+
+func TestHashMap_GetOrDefault(t *testing.T) {
+	t.Parallel()
+
+	assert := internal.NewAssert(t, "TestHashMap_GetOrDefault")
+
+	hm := NewHashMap()
+
+	hm.Put("a", 1)
+	hm.Put("b", 2)
+	hm.Put("c", 3)
+
+	assert.Equal(1, hm.GetOrDefault("a", 5))
+	assert.Equal(5, hm.GetOrDefault("d", 5))
+}