Publish/Subscribe API for Go SDK

The foundation of the PubNub service is the ability to send a message and have it delivered anywhere in less than 30ms. Send a message to just one other person, or broadcast to thousands of subscribers at once.

For higher-level conceptual details on publishing and subscribing, refer to Connection Management and to Publish Messages.

Publish​

The Publish() method sends a message to all channel subscribers. A successfully published message is replicated across PubNub's points of presence and sent simultaneously to all subscribed clients on a channel.

  • You must initialize PubNub with the publishKey.
  • You don't have to be subscribed to a channel to publish to it.
  • You cannot publish to multiple channels simultaneously.

Method(s)​

To Publish a message you can use the following method(s) in the Go SDK:

pn.Publish().
    Message(interface{}).
    Channel(string).
    ShouldStore(bool).
    UsePost(bool).
    Meta(interface{}).
    QueryParam(queryParam).
    CustomMessageType(string).
    Execute()
* required
ParameterDescription
Message *
Type: interface
Default:
n/a
The payload
Channel *
Type: string
Default:
n/a
Destination of Message (channel ID)
ShouldStore
Type: bool
Default:
account default
Store in history
UsePost
Type: bool
Default:
false
Use POST to Publish
Meta
Type: interface
Default:
null
Meta data object which can be used with the filtering ability
TTL
Type: int
Default:
n/a
Set a per message time to live in Message Persistence.
  1. If ShouldStore = true, and TTL = 0, the message is stored with no expiry time.
  2. If ShouldStore = true and TTL = X (X is an Integer value), the message is stored with an expiry time of X hours unless you have message retention set to Unlimited on your keyset configuration in the Admin Portal.
  3. If ShouldStore = false, the TTL parameter is ignored.
  4. If TTL is not specified, then expiration of the message defaults back to the expiry value for the key.
QueryParam
Type: map[string]string
Default:
nil
QueryParam accepts a map, the keys and values of the map are passed as the query string parameters of the URL called by the API.
CustomMessageType
Type: string
Default:
n/a
A case-sensitive, alphanumeric string from 3 to 50 characters describing the business-specific label or category of the message. Dashes - and underscores _ are allowed. The value cannot start with special characters or the string pn_ or pn-.

Examples: text, action, poll.

Sample code​

Reference code

This example is a self-contained code snippet ready to be run. It includes necessary imports and executes methods with console logging. Use it as a reference when working with other examples in this document.

Publish a message to a channel​

package main

import (
    "fmt"
    pubnub "github.com/pubnub/go/v7"
)

func main() {
    config := pubnub.NewConfigWithUserId("myUniqueUserId")
    config.SubscribeKey = "demo"
    config.PublishKey = "demo"
    pn := pubnub.NewPubNub(config)

    message := []string{"Hello", "there"}

show all 31 lines
Subscribe to the channel

Before running the above publish example, either using the Debug Console or in a separate script running in a separate terminal window, subscribe to the same channel that is being published to.

Response​

MethodDescription
Timestamp
Type: int
An int representation of the timetoken when the message was published

Other examples​

Publish with metadata​

res, status, err := pn.Publish().
    Channel("my-channel").
    Message([]string{"Hello", "there"}).
    Meta(map[string]interface{}{
        "name": "Alex",
    }).
    CustomMessageType("text-message").
    Execute()

Publish array​

res, status, err := pn.Publish().
    Channel("my-channel").
    Message([]string{"Hello", "there"}).
    Meta([]string{"1a", "2b", "3c"}).
    CustomMessageType("text-message").
    Execute()

Store the published message for 10 hours​

res, status, err := pn.Publish().
    Channel("my-channel").
    Message("test").
    ShouldStore(true).
    TTL(10).
    CustomMessageType("text-message").
    Execute()

Push payload helper​

You can use the helper method as an input to the Message parameter, to format the payload for publishing Push messages. For more info on the helper method, check Create Push Payload Helper Section

aps := pubnub.PNAPSData{
    Alert: "apns alert",
    Badge: 1,
    Sound: "ding",
    Custom: map[string]interface{}{
        "aps_key1": "aps_value1",
        "aps_key2": "aps_value2",
    },
}

apns := pubnub.PNAPNSData{
    APS: aps,
    Custom: map[string]interface{}{
        "apns_key1": "apns_value1",
        "apns_key2": "apns_value2",
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Fire​

The fire endpoint allows the client to send a message to Functions Event Handlers and Illuminate. These messages will go directly to any Event Handlers registered on the channel that you fire to and will trigger their execution. The content of the fired request will be available for processing within the Event Handler. The message sent via fire() isn't replicated, and so won't be received by any subscribers to the channel. The message is also not stored in history.

Method(s)​

To Fire a message you can use the following method(s) in the Go SDK:

pn.Fire().
    Message(interface{}).
    Channel(string).
    UsePost(bool).
    Meta(interface{}).
    QueryParam(queryParam).
    Execute()
* required
ParameterDescription
Message *
Type: interface
Default:
n/a
The payload
Channel *
Type: string
Default:
n/a
Destination of Message (channel ID)
UsePost
Type: bool
Default:
false
Use POST to Publish
Meta
Type: interface
Default:
null
Meta data object which can be used with the filtering ability
TTL
Type: int
Default:
n/a
Set a per message time to live in Message Persistence.
  1. If ShouldStore = true, and TTL = 0, the message is stored with no expiry time.
  2. If ShouldStore = true and TTL = X (X is an Integer value), the message is stored with an expiry time of X hours unless you have message retention set to Unlimited on your keyset configuration in the Admin Portal.
  3. If ShouldStore = false, the TTL parameter is ignored.
  4. If TTL is not specified, then expiration of the message defaults back to the expiry value for the key.
QueryParam
Type: map[string]string
Default:
nil
QueryParam accepts a map, the keys and values of the map are passed as the query string parameters of the URL called by the API.

Sample code​

Fire a message to a channel​

res, status, err := pn.Fire().
            Channel("my-channel").
            Message("test").
            Execute()

Signal​

The signal() function is used to send a signal to all subscribers of a channel.

By default, signals are limited to a message payload size of 64 bytes. This limit applies only to the payload, and not to the URI or headers. If you require a larger payload size, please contact support.

Method(s)​

To Signal a message you can use the following method(s) in the Go SDK:

pubnub.Signal().
    Message(interface{}).
    Channel(string).
    CustomMessageType(string).
    Execute()
* required
ParameterDescription
Message *
Type: interface
Default:
n/a
The payload.
Channel *
Type: string
Default:
n/a
Destination of Message (channel ID).
CustomMessageType
Type: string
Default:
n/a
A case-sensitive, alphanumeric string from 3 to 50 characters describing the business-specific label or category of the message. Dashes - and underscores _ are allowed. The value cannot start with special characters or the string pn_ or pn-.

Examples: text, action, poll.

Sample code​

Signal a message to a channel​

result, status, err := pubnub.Signal().
    Message([]string{
        "Hello", "Signals"
    }).
    Channel("foo").
    CustomMessageType("text-message").
    Execute();

Response​

MethodDescription
Timestamp
Type: int
An int representation of the timetoken when Signal was sent

Subscribe​

Receive messages​

Your app receives messages and events via event listeners. The event listener is a single point through which your app receives all the messages, signals, and events that are sent in any channel you are subscribed to.

For more information about adding a listener, refer to the Event Listeners section.

Description​

This function causes the client to create an open TCP socket to the PubNub Real-Time Network and begin listening for messages on a specified channel ID. To subscribe to a channel ID the client must send the appropriate SubscribeKey at initialization. By default a newly subscribed client will only receive messages published to the channel after the Subscribe() call completes.

Connectivity notification

You can be notified of connectivity via the envelope.status. By waiting for the envelope.status to return before attempting to publish, you can avoid a potential race condition on clients that subscribe and immediately publish messages before the subscribe has completed.

Using Go SDK, if a client becomes disconnected from a channel, it can automatically attempt to reconnect to that channel and retrieve any available messages that were missed during that period by setting restore to true. By default a client will attempt to reconnect after exceeding a 320 second connection timeout.

Unsubscribing from all channels

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)​

To Subscribe to a channel you can use the following method(s) in the Go SDK:

pn.Subscribe().
    Channels([]string).
    ChannelGroups([]string).
    Timetoken(int64).
    WithPresence(bool).
    QueryParam(queryParam).
    Execute()
* required
ParameterDescription
Channels
Type: []string
Subscribe to channels, Either channel ID or channel_group is required.
ChannelGroups
Type: []string
Subscribe to channel_groups, Either channel ID or channel_group is required.
Timetoken
Type: int64
Pass a timetoken.
WithPresence
Type: bool
Also subscribe to related presence information.

For information on how to receive presence events and what those events are, refer to Presence Events.
QueryParam
Type: map[string]string
QueryParam accepts a map, the keys and values of the map are passed as the query string parameters of the URL called by the API.

Sample code​

Subscribe to a channel:

pn.Subscribe().
    Channels([]string{"my-channel"}). // subscribe to channels
    Execute()

Response​

PNMessage

PNMessage is returned in the Listeners

The Subscribe() operation returns a PNStatus which contains the following operations:

Property NameTypeDescription
Category
StatusCategory
Details of StatusCategory are here
Error
bool
This is true if an error occurred in the execution of the operation.
ErrorData
error
Error data of the exception (if Error is true).
StatusCode
int
Status code of the execution.
Operation
OperationType
Operation type of the request.

The Subscribe() operation returns a PNMessage for messages, for both Publish and Signal messages, which contains the following operations:

MethodDescription
Message
Type: interface
The message sent on the channel ID.
Channel
Type: string
The channel ID on which the message was received.
Subscription
Type: string
The channel group or wildcard subscription match (if exists).
Timetoken
Type: int64
Timetoken for the message.
UserMetadata
Type: interface
User metadata.
SubscribedChannel
Type: string
Current subscribed channel.
Publisher
Type: string
UUID of publisher.

The Subscribe() operation returns a PNPresence for messages which contains the following operations:

MethodDescription
Event
Type: string
Events like join, leave, timeout, state-change.
UUID
Type: string
UUID for event.
Timestamp
Type: int64
Timestamp for event.
Occupancy
Type: int
Current occupancy.
Subscription
Type: string
Message has been received on the Channel ID.
Timetoken
Type: int64
Timetoken of the message.
State
Type: interface
State of the UUID.
UserMetadata
Type: map[string]interface
User metadata.
SubscribedChannel
Type: string
Current subscribed channel.
Channel
Type: string
The channel ID for which the message belongs.

The Subscribe() operation returns a PNUUIDEvent for UUID Events which contains the following operations:

MethodDescription
Event
Type: PNObjectsEvent
Events like PNObjectsEventRemove, PNObjectsEventSet.
Timestamp
Type: string
Timestamp for event.
Subscription
Type: string
Event has been received on the Channel ID.
SubscribedChannel
Type: string
Current subscribed channel.
Channel
Type: string
The channel ID for which the event belongs.
UUID
Type: string
The UUID.
Name
Type: string
Display name for the space.
ExternalID
Type: string
User's identifier in an external system
ProfileURL
Type: string
The URL of the user's profile picture
Email
Type: string
The user's email address.
Custom
Type: map[string]interface
Map of string and interface with supported data types.
Updated
Type: string
Last updated date.
ETag
Type: string
The ETag.

The Subscribe() operation returns a PNChannelEvent for Channel Events which contains the following operations:

MethodDescription
Event
Type: PNObjectsEvent
Events like PNObjectsEventRemove, PNObjectsEventSet.
Timestamp
Type: string
Timestamp for event.
Subscription
Type: string
Event has been received on the Channel ID.
SubscribedChannel
Type: string
Current subscribed channel.
Channel
Type: string
The channel ID for which the event belongs.
ChannelID
Type: string
The Channel ID.
Name
Type: string
Display name for the space.
Description
Type: string
Description of the space.
Custom
Type: map[string]interface
Map of string and interface with supported data types.
Updated
Type: string
Last updated date.
ETag
Type: string
The ETag.

The Subscribe() operation returns a PNMembershipEvent for Membership Events which contains the following operations:

MethodDescription
Event
Type: PNObjectsEvent
Events like PNObjectsEventRemove, PNObjectsEventSet.
Timestamp
Type: string
Timestamp for event.
Subscription
Type: string
Event has been received on the Channel ID.
SubscribedChannel
Type: string
Current subscribed channel.
Channel
Type: string
The channel ID for which the event belongs.
ChannelID
Type: string
The Channel ID.
UUID
Type: string
The UUID.
Custom
Type: map[string]interface
Map of string and interface with supported data types.

The Subscribe() operation returns a PNMessageActionsEvent for Message Actions Events which contains the following operations:

MethodDescription
Event
Type: PNMessageActionsEventType
Events like PNMessageActionsAdded, PNMessageActionsRemoved.
Data
Type: PNMessageActionsResponse
Message Actions for event.
Subscription
Type: string
Event has been received on the Channel ID.
SubscribedChannel
Type: string
Current subscribed channel.
Channel
Type: string
The channel ID for which the event belongs.

Other examples​

Basic subscribe with logging​

import (
    pubnub "github.com/pubnub/go"
)

config := pubnub.NewConfig()
// publishKey from admin panel (only required if publishing)
config.PublishKey = "demo" // required
// subscribeKey from admin panel
config.SubscribeKey = "demo"

pn := pubnub.NewPubNub(config)

pn.Subscribe().
    Channels([]string{"my-channel"}).
    Execute()

Subscribing to multiple channels​

It's possible to subscribe to more than one channel using the Multiplexing feature. The example shows how to do that using an array to specify the channel names.

Alternative subscription methods

You can also use Wildcard Subscribe and Channel Groups to subscribe to multiple channels at a time. To use these features, the Stream Controller add-on must be enabled on your keyset in the Admin Portal.

import (
    pubnub "github.com/pubnub/go"
)

pn.Subscribe().
    Channels([]string{"my-channel1", "my-channel2"}).
    Execute()

Subscribing to a Presence channel​

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

For any given channel there is an associated Presence channel. You can subscribe directly to the channel by appending -pnpres to the channel name. For example the channel named my_channel would have the presence channel named my_channel-pnpres.

pn.Subscribe().
    Channels([]string{"my-channel"}).
    WithPresence(true).
    Execute()

Sample Responses​

Join event​
if presence.Event == "join" {
    presence.UUID // 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}
Leave event​
if presence.Event == "leave" {
    presence.UUID // 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}
Timeout event​
if presence.Event == "timeout" {
    presence.UUID // 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}
State change event​
if presence.Event == "state-change" {
    presence.Timestamp
    presence.Occupancy
}
Interval event​
if presence.Event == "interval" {
    presence.UUID // 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}

When a channel is in interval mode with presence_deltas pnconfig flag enabled, the interval message may also include the following fields which contain an array of changed UUIDs since the last interval message.

  • joined
  • left
  • timedout

For example, this interval message indicates there were 2 new UUIDs that joined and 1 timed out UUID since the last interval:

if presence.Event == "interval" {
    presence.Occupancy // # users in channel
    presence.Join // [uuid1 uuid2]
    presence.Timeout //[uuid3]
    presence.Timestamp // unix timestamp
}

If the full interval message is greater than 30KB (since the max publish payload is ∼32KB), none of the extra fields will be present. Instead there will be a here_now_refresh boolean field set to true. This indicates to the user that they should do a hereNow request to get the complete list of users present in the channel.

Wildcard subscribe to channels​

Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal (with Enable Wildcard Subscribe checked). Read the support page on enabling add-on features on your keys.

Wildcard subscribes allow the client to subscribe to multiple channels using wildcard. For example, if you subscribe to a.* you will get all messages for a.b, a.c, a.x. The wildcarded * portion refers to any portion of the channel string name after the dot (.).

import (
    pubnub "github.com/pubnub/go"
)

pn.Subscribe().
    Channels([]string{"foo.*"}). // subscribe to channels information
    Execute()
Wildcard grants and revokes

Only one level (a.*) of wildcarding is supported. If you grant on * or a.b.*, the grant will treat * or a.b.* as a single channel named either * or a.b.*. You can also revoke permissions from multiple channels using wildcards but only if you previously granted permissions using the same wildcards. Wildcard revokes, similarly to grants, only work one level deep, like a.*.

Subscribing with state​

Requires Presence

This method requires that the Presence add-on is enabled for your key in the Admin Portal.

For information on how to receive presence events and what those events are, refer to Presence Events.

Required UUID

Always set the UUID to uniquely identify the user or device that connects to PubNub. This UUID should be persisted, and should remain unchanged for the lifetime of the user or the device. If you don't set the UUID, you won't be able to connect to PubNub.

import (
    pubnub "github.com/pubnub/go"
)

config := pubnub.NewConfig()
config.SubscribeKey = "demo"
config.PublishKey = "demo"

pn := pubnub.NewPubNub(config)

listener := pubnub.NewListener()
done := make(chan bool)

go func() {
    for {
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Subscribe to a channel group​

Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

import (
    pubnub "github.com/pubnub/go"
)

pn.Subscribe().
    Channels([]string{"ch1", "ch2"}). // subscribe to channels
    ChannelGroups([]string{"cg1", "cg2"}). // subscribe to channel groups
    Timetoken(int64(1337)). // optional, pass a timetoken
    WithPresence(true). // also subscribe to related presence information
    Execute()

Subscribe to the Presence channel of a channel group​

Requires Stream Controller and Presence add-ons

This method requires both the Stream Controller and Presence add-ons are enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

import (
    pubnub "github.com/pubnub/go"
)

pn.Subscribe().
    ChannelGroups([]string{"cg1", "cg2"}). // subscribe to channel groups
    Timetoken(int64(1337)). // optional, pass a timetoken
    WithPresence(true). // also subscribe to related presence information
    Execute()

Unsubscribe​

When subscribed to a single channel, this function causes the client to issue a leave from the channel and close any open socket to the PubNub Network. For multiplexed channels, the specified channel(s) will be removed and the socket remains open until there are no more channels remaining in the list.

Unsubscribing from all channels

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)​

To Unsubscribe from a channel you can use the following method(s) in the Go SDK:

pn.Unsubscribe().
    Channels([]string).
    ChannelGroups([]string).
    QueryParam(queryParam).
    Execute()
* required
ParameterDescription
Channels
Type: []string
Default:
false
Unsubscribe to channels, Either channel ID or channelGroup is required.
ChannelGroups
Type: []string
Default:
false
Unsubscribe to channel groups, Either channel ID or channelGroup is required.
QueryParam
Type: map[string]string
Default:
nil
QueryParam accepts a map, the keys and values of the map are passed as the query string parameters of the URL called by the API.

Sample code​

Unsubscribe from a channel:

pn.Unsubscribe().
    Channels([]string{"my-channel"}).
    Execute()
Event listeners

The response of the subscription is handled by Listener. Please see the Listeners section for more details.

Rest response from server​

The output below demonstrates the response to a successful call:

if presence.Event == "leave" {
    presence.UUID // left-uuid
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}

Other examples​

Unsubscribing from multiple channels​

Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

import (
    pubnub "github.com/pubnub/go"
)

pn.Unsubscribe().
    Channels([]string{"my-channel", "my-channel2"}).
    Execute()
Example response​
if presence.Event == "leave" {
    presence.UUID // left-uuid
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}

Unsubscribe from a channel group​

import (
    pubnub "github.com/pubnub/go"
)

pn.Unsubscribe().
    ChannelGroups([]string{"cg1", "cg2"}).
    Execute()

Example Response: 

if presence.Event == "leave" {
    presence.UUID // left-uuid
    presence.Timestamp // 1345546797
    presence.Occupancy // 2
}

Unsubscribe all​

Unsubscribe from all channels and all channel groups

Method(s)​

UnsubscribeAll()

Sample code​

pn.UnsubscribeAll()

Returns​

None

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