Remove entire subscription model

It was a valiant effort, and the implementation was solid and
dependable, but at the end of the day we can achieve the same
functionality in a much simpler fashion with commands, especially
because Go is not held to the same restrictions as Elm.

examples/simple/main.go

@@ -13,7 +13,7 @@ import (
 // A model can be more or less any type of data. It holds all the data for a
 // program, so often it's a struct. For this simple example, however, all
 // we'll need is a simple integer.
-type Model int
+type model int
 
 // Messages are events that we respond to in our Update function. This
 // particular one indicates that the timer has ticked.
@@ -21,22 +21,22 @@ type tickMsg time.Time
 
 func main() {
 	// Initialize our program
-	p := boba.NewProgram(initialize, update, view, subscriptions)
+	p := boba.NewProgram(initialize, update, view)
 	if err := p.Start(); err != nil {
 		log.Fatal(err)
 	}
 }
 
 func initialize() (boba.Model, boba.Cmd) {
-	return Model(5), nil
+	return model(5), tick
 }
 
 // Update is called when messages are recived. The idea is that you inspect
 // the message and update the model (or send back a new one) accordingly. You
 // can also return a commmand, which is a function that peforms I/O and
 // returns a message.
-func update(msg boba.Msg, model boba.Model) (boba.Model, boba.Cmd) {
-	m, _ := model.(Model)
+func update(msg boba.Msg, mdl boba.Model) (boba.Model, boba.Cmd) {
+	m, _ := mdl.(model)
 
 	switch msg.(type) {
 	case boba.KeyMsg:
@@ -46,23 +46,19 @@ func update(msg boba.Msg, model boba.Model) (boba.Model, boba.Cmd) {
 		if m <= 0 {
 			return m, boba.Quit
 		}
+		return m, tick
 	}
 	return m, nil
 }
 
 // Views take data from the model and return a string which will be rendered
 // to the terminal.
-func view(model boba.Model) string {
-	m, _ := model.(Model)
+func view(mdl boba.Model) string {
+	m, _ := mdl.(model)
 	return fmt.Sprintf("Hi. This program will exit in %d seconds. To quit sooner press any key.\n", m)
 }
 
-// This is a subscription which we setup in NewProgram(). It waits for one
-// second, sends a tick, and then restarts.
-func subscriptions(_ boba.Model) boba.Subs {
-	return boba.Subs{
-		"tick": boba.Every(time.Second, func(t time.Time) boba.Msg {
-			return tickMsg(t)
-		}),
-	}
+func tick() boba.Msg {
+	time.Sleep(time.Second)
+	return tickMsg{}
 }