fix(tea): allocate msgs channel in constructor

Race condition bug: Start() is called in a new gorotuine, then Send(). If the
Send happens before the msgs channel is allocated, the message is dropped.

Instead allocate the channel in the constructor, so msgs is never nil.

Signed-off-by: Christian Stewart <christian@paral.in>

tea.go

@@ -239,6 +239,7 @@ func NewProgram(model Model, opts ...ProgramOption) *Program {
 		initialModel: model,
 		output:       os.Stdout,
 		input:        os.Stdin,
+		msgs:         make(chan Msg),
 		CatchPanics:  true,
 	}
 
@@ -252,8 +253,6 @@ func NewProgram(model Model, opts ...ProgramOption) *Program {
 
 // StartReturningModel initializes the program. Returns the final model.
 func (p *Program) StartReturningModel() (Model, error) {
-	p.msgs = make(chan Msg)
-
 	var (
 		cmds = make(chan Cmd)
 		errs = make(chan error)
@@ -554,9 +553,7 @@ func (p *Program) Start() error {
 // This method is currently provisional. The method signature may alter
 // slightly, or it may be removed in a future version of this package.
 func (p *Program) Send(msg Msg) {
-	if p.msgs != nil {
-		p.msgs <- msg
-	}
+	p.msgs <- msg
 }
 
 // Quit is a convenience function for quitting Bubble Tea programs. Use it