Go (golang) package for writing bots on the Facebook Messenger Platform.

• Fluent API makes building messages easy.
• Timeoutable, cancellable requests using context.Context.
• Designed for use with one or many subscribed pages.

go get gopkg.in/ekyoung/fbmessenger.v1

The primary types in the package are CallbackDispatcher and Client. CallbackDispatcher is used to handle the callbacks Facebook sends to your webhook endpoint. Client is used to send messages and to get user profiles.

Unmarshal the json received at your webhook endpoint into an instance of type Callback.

cb := &fbmessenger.Callback{}
err := json.Unmarshal(requestBytes, cb)

Use type CallbackDispatcher to route each MessagingEntry included in the callback to an appropriate handler for the type of entry. Note that due to webhook batching, a handler may be called more than once per callback.

dispatcher := &fbmessenger.CallbackDispatcher{
	MessageHandler: MessageReceived
}

err := dispatcher.Dispatch(cb)

Callback handlers should have a signature mathing the MessageEntryHandler type.

func MessageReceived(cb *fbmessenger.MessagingEntry) error {
	//Do stuff
}

Create a Client to make requests to the messenger API.

client := fbmessenger.Client{}

There are structs for the different types of messages you can send. The easiest way to create them is with the fluent API.

request := fbmessenger.TextMessage("Hello, world!").To("USER_ID")

Then send your request and handle errors in sending, and errors returned from Facebook.

response, err := client.Send(request, "YOUR_PAGE_ACCESS_TOKEN")
if err != nil {
	//Got an error. Request never got to Facebook.
} else if response.Error != nil {
	//Request got to Facebook. Facebook returned an error.
} else {
	//Hooray!
}

Get a user's profile using their userId.

userProfile, err := client.GetUserProfile("USER_ID", "YOUR_PAGE_ACCESS_TOKEN")

For more control over requests (timeouts, etc.) use the *WithContext version of the above methods.

ctx, _ := context.WithTimeout(context.Background(), 500*time.Millisecond)
response, err := client.SendWithContext(ctx, request, "YOUR_PAGE_ACCESS_TOKEN")
userProfile, err := userProfileGetter.GetUserProfileWithContext(ctx, "USER_ID", "YOUR_PAGE_ACCESS_TOKEN")

Some ideas where pulled from Go Client Library Best Practices by Jack Lindamood.