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Server Sent Events (SSE)#

The sse package provides a helper for streaming Server-Sent Events (SSE) responses.

SSE is a simple protocol for sending events from the server to the client over HTTP. It is a one-way protocol, meaning that the client cannot send events to the server, but can consume them as they are sent. It is popularly used as a push mechanism for web and other clients.


The sse package provides a simple API for sending events to the client and documents the event types and data structures in the OpenAPI spec if you provide a mapping of message type names to Go structs:

// Register using sse.Register instead of huma.Register
sse.Register(api, huma.Operation{
	OperationID: "sse",
	Method:      http.MethodGet,
	Path:        "/sse",
	Summary:     "Server sent events example",
}, map[string]any{
	// Mapping of event type name to Go struct for that event.
	"message":      DefaultMessage{},
	"userCreate":   UserCreatedEvent{},
	"mailReceived": MailReceivedEvent{},
}, func(ctx context.Context, input *struct{}, send sse.Sender) {
	// Send an event every second for 10 seconds.
	for x := 0; x < 10; x++ {
		send.Data(MailReceivedEvent{UserID: "abc123"})
		time.Sleep(1 * time.Second)

Type Reuse

Each event model must be a unique Go type. If you want to reuse Go type definitions, you can define a new type referencing another type, e.g. type MySpecificEvent MyBaseEvent and it will work as expected.

Sending Data#

The send Sender passed to your SSE operation handler provides several ways of sending data to the client:

Method Description
send(Message) Send an event using a full message struct
send.Data(any) Send a message with the given data

Unless you need to set the message ID or retry information, the send.Data(any) method is preferred.

Dive Deeper#