doc: add doc for Pipeline function

function/function.go

@@ -113,3 +113,15 @@ func Schedule(d time.Duration, fn interface{}, args ...interface{}) chan bool {
 
 	return quit
 }
+
+// Pipeline takes a list of functions and returns a function whose param will be passed into
+// the functions one by one.
+func Pipeline(funcs ...func(interface{}) interface{}) func(interface{}) interface{} {
+	return func(arg interface{}) (result interface{}) {
+		result = arg
+		for _, fn := range funcs {
+			result = fn(result)
+		}
+		return
+	}
+}

function/function_test.go

@@ -130,3 +130,21 @@ func TestSchedule(t *testing.T) {
 	expected := []string{"*", "*", "*", "*", "*"}
 	assert.Equal(expected, res)
 }
+
+func TestPipeline(t *testing.T) {
+	assert := internal.NewAssert(t, "TestPipeline")
+
+	addOne := func(x interface{}) interface{} {
+		return x.(int) + 1
+	}
+	double := func(x interface{}) interface{} {
+		return 2 * x.(int)
+	}
+	square := func(x interface{}) interface{} {
+		return x.(int) * x.(int)
+	}
+
+	f := Pipeline(addOne, double, square)
+
+	assert.Equal(36, f(2))
+}