pipeline := Command("echo", "this is a main test").
	Pipe(Func(func(input, output chan (string)) {
		for i := range input {
			t.Log("myfunc say : ", i, "\n")
			output <- i
		}
		close(output)
	})).
	Pipe(Command("sed", "s/main/lame/g")).
	Pipe(Command("grep", "test"))

output, _ := pipeline.Run()

for i := range output {
	t.Log(i)
	if i != "this is a lame test\n" {
		t.Error("Expected this is a lame test, got ", i)
	}
}

./main.go 
myfunc say : this is a main test
this is a lame test