refactor: sort (#21)

Removed reverse func because it use to much cpu and add test cas for asc sort

slice/slice_test.go

@@ -381,7 +381,7 @@ func TestDifference(t *testing.T) {
 	assert.Equal([]int{1, 2, 3}, Difference(s1, s2))
 }
 
-func TestSortByField(t *testing.T) {
+func TestSortByFieldDesc(t *testing.T) {
 	assert := internal.NewAssert(t, "TestSortByField")
 
 	type student struct {
@@ -406,6 +406,31 @@ func TestSortByField(t *testing.T) {
 
 	assert.Equal(students, studentsOfSortByAge)
 }
+func TestSortByFieldAsc(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSortByField")
+
+	type student struct {
+		name string
+		age  int
+	}
+	students := []student{
+		{"a", 10},
+		{"b", 15},
+		{"c", 5},
+		{"d", 6},
+	}
+	studentsOfSortByAge := []student{
+		{"c", 5},
+		{"d", 6},
+		{"a", 10},
+		{"b", 15},
+	}
+
+	err := SortByField(students, "age")
+	assert.IsNil(err)
+
+	assert.Equal(students, studentsOfSortByAge)
+}
 
 func TestWithout(t *testing.T) {
 	assert := internal.NewAssert(t, "TestWithout")