Revel Hello World app

app.go

package controllers

import "github.com/robfig/revel"

type App struct {
   *revel.Controller
}

func (c App) Index() revel.Result {
   greeting := "Hello woooooorld!"
   return c.Render(greeting)
}

func (c App) Hello(myName string) revel.Result {
   c.Validation.Required(myName).Message("Your name is required!")
   c.Validation.MinSize(myName, 3).Message("Your name is not long enough.")

   if c.Validation.HasErrors() {
      c.Validation.Keep()
      c.FlashParams()
      return c.Redirect(App.Index)
   }   

   return c.Render(myName)
}

Hello.html

{{set . "title" "Home"}}                                                                                              
{{template "header.html" .}}                                                                                          
                                                                                                                      
<h1>Hello {{.myName}}</h1>                                                                                            
<a href="/">Back to form</a>                                                                                          
                                                                                                                      
{{template "footer.html" .}} 

Index.html

{{set . "title" "Home"}}
{{template "header.html" .}} 

<h1>{{ .greeting }}</h1>

{{range .errors}}
   <p class="alert">{{.Message}}</p>
{{end}}

<form action="/App/Hello" method="GET">
   <input id="" name="myName" type="text" />
   <input type="submit" value="Say Hello!" />
</form>

{{template "footer.html" .}} 

Would you mind telling me how to run this app.go?
I tried

% revel run app.go
% revel run app

both of these failed with following message

ERROR 2013/09/18 03:14:16 revel.go:239: Failed to import app with error: cannot find package "app" in any of:
        /home/hiromu/go/src/pkg/app (from $GOROOT)
        /home/hiromu/go/.packages/src/app (from $GOPATH)

Do I have to set this app in $GOPATH?