Worked out the docs for the email sending feature.

README.md

@@ -474,14 +474,94 @@ When you start with the UI can you can prototype all of the interactions, figure
 aim for only what you need. Keep doing this and you'll slowly build a nice data model with less
 cruft for the application you're creating.
 
-
 ## Additional Features
 
-### Sending Emails
+## Sending Emails
 
-Coming soon...
+> __WARNING__: The email sending feature is currently very simple. Don't think you can send 200
+> million spam messages with it.
+
+The email system uses a [Redis]() queue to schedule messages, and an email router to actually
+deliver them.  The idea is that you don't want to wait for email crafting and delivery in your web
+application most of the time.  Ideally what you want to do is:
+
+1. In an `api.go` you receive a form or action from the user that needs an email. Say a password
+   reset.
+2. You use the `common/email` module to craft a simple message and send it to the queue. Your
+   message at this stage is usually a very simple `struct` with the information your email router
+   needs to build the email.
+3. In your `api.go` file _immediately return rather than wait for email delivery._
+4. Your email router then sits there and processes the email requests. When a new message comes in
+   it takes the data, queries your database, configures the templates, and finally sends it to the
+   email server.
+
+Since email is asynchronous there's no point in your web application waiting around for all of #4 to
+be done.  Just toss out a message on a queue and move on.
+
+### Running the `mailer`
+
+There's a simple router implemented in `tools/cmd/mailer` that you can run to get going.  You can
+use this to send simple emails but you should probably write a new one that handles your more
+sophisticated emails like password resets and receipts.
+
+You can run it from the command line with:
+
+```shell
+./bin/mailer
+```
+
+It will require that you install `redis` for it to work.
+
+### Testing Your Email Locally
+
+Running an email server locally is kind of a pain, and setting up everything so you can view sent
+emails is even harder. That's way the awesome and fabulous [MailHog](https://github.com/mailhog/MailHog) exists.
+
+You can install it easily (it's written in Go) and then run it:
+
+```shell
+MailHog
+```
+
+By default it opens an SMTP port on `1025` and a web server at 127.0.0.1:8025. If you point your
+browser at 127.0.0.:8025 you'll get a fake email inbox. This inbox will show you both the HTML and
+TEXT versions of your email, plus other useful things.
+
+### How To Send
 
-### Receiving Payments
+Here's an example of sending an email from a form submission in `features/email/api.go`.
+
+```go
+package features_email
+
+import (
+  email "MY/webapp/common/email"
+  "github.com/gofiber/fiber/v2"
+)
+
+func PostApiEmailSend(c *fiber.Ctx) error {
+  go email.OneShotSend(email.EmailMessage{
+    To: c.FormValue("To"),
+    From: c.FormValue("From"),
+    Subject: c.FormValue("Subject"),
+    Template: c.FormValue("Template"),
+  })
+
+  return c.Redirect("/email/")
+}
+
+func SetupApi(app *fiber.App) {
+  app.Post("/api/email/send", PostApiEmailSend)
+}
+```
+
+### Email Templates
+
+The templates use the same default `text/template` engine that the rest of the system uses, but you
+should use Markdown to write them. This automatically gives you both a nice text format (Markdown
+already is like an email) and an HTML output.  Look at `emails/signup.md` for a simple example.
+
+## Receiving Payments
 
 Coming soon...
 
@@ -489,6 +569,15 @@ Coming soon...
 
 Here's some questions I get when people see this.
 
+### What if My Email Templates Need HTML?
+
+You should be able to work with the code in `common/email` to make it do what you want. I don't
+think it's specifically looking for any extension, but I haven't tested it.  Try just dropping the
+`.html` you want into the `emails/` directory and sending it.
+
+You should also know that really complex HTML usually get filtered, so it's best to keep it simple
+HTML and Markdown will help you stick to that.
+
 ### Isn't Fiber Banned?!
 
 First off, nobody has the right to "ban" a project.  If you're hanging out in the Go discord and

common/email/api.go

@@ -98,7 +98,7 @@ func (router *Router) DeliverEmail(msg EmailMessage) error {
   }
 
   log.Println("template is", msg.Template)
-  text, html, err := router.Render(msg.Template, nil)
+  text, html, err := router.Render(msg.Template, msg)
   if err != nil { return err }
 
   email_msg.SetBodyString(mail.TypeTextHTML, html)
@@ -150,6 +150,8 @@ func (sender *Sender) QueueEmail(msg EmailMessage) error {
   return nil
 }
 
+// Intended to be fired off on a goroutine and
+// forgotten about.
 func OneShotSend(msg EmailMessage) {
   ctx := context.Background()
 

common/email/data.go

@@ -24,6 +24,5 @@ type Router struct {
   redis_client *redis.Client
   smtp_client *mail.Client
   ctx context.Context
-
 }
 

emails/signup.md

@@ -1,4 +1,10 @@
 Welcome
 =======
 
-Welcome to my website!
+Welcome to my website!  Here's what you sent:
+
+* {{ .From }}
+* {{ .To }}
+* {{ .Data.Name }}
+* {{ .Data.Pet }}
+

features/init.go

@@ -6,7 +6,6 @@ import (
   "MY/webapp/features/paypal"
   "MY/webapp/features/shopping"
   "MY/webapp/features/fakepay"
-  "MY/webapp/features/myfeature"
 )
 
 func Setup(app *fiber.App) {
@@ -14,5 +13,4 @@ func Setup(app *fiber.App) {
   features_paypal.Setup(app)
   features_shopping.Setup(app)
   features_fakepay.Setup(app)
-  features_myfeature.Setup(app)
 }

tools/cmd/qmgr/main.go

@@ -7,6 +7,11 @@ import (
   "fmt"
 )
 
+type Person struct {
+  Name string
+  Pet string
+}
+
 func main() {
   config.Load("config.json")
 
@@ -17,6 +22,10 @@ func main() {
     From: "toni.sender@example.com",
     Subject: "This is my first mail.",
     Template: "signup.md",
+    Data: Person{
+      Name: "Zed",
+      Pet: "None",
+    },
   }
 
   fmt.Println("sending", msg)