Go Libraries

Go libraries for implementing ActivityPub.

go-fed/activity

Comprehensive ActivityPub/ActivityStreams implementation.

Property	Value
Repository	github.com/go-fed/activity
Documentation	go-fed.org
License	BSD-3
Status	Active

Features

• Complete ActivityStreams vocabulary
• ActivityPub C2S and S2S
• HTTP Signatures
• Extensible type system

Example

package main

import (
    "github.com/go-fed/activity/streams"
    "github.com/go-fed/activity/streams/vocab"
)

func createNote() vocab.ActivityStreamsNote {
    note := streams.NewActivityStreamsNote()

    // Set content
    contentProp := streams.NewActivityStreamsContentProperty()
    contentProp.AppendXMLSchemaString("Hello from Go!")
    note.SetActivityStreamsContent(contentProp)

    // Set attributedTo
    attrProp := streams.NewActivityStreamsAttributedToProperty()
    attrProp.AppendIRI(actorIRI)
    note.SetActivityStreamsAttributedTo(attrProp)

    return note
}

S2S Federation

import "github.com/go-fed/activity/pub"

// Implement required interfaces
type myActor struct{}

func (a *myActor) PostInbox(c context.Context, w http.ResponseWriter, r *http.Request) (bool, error) {
    // Handle incoming activities
}

func (a *myActor) GetOutbox(c context.Context, w http.ResponseWriter, r *http.Request) (bool, error) {
    // Return outbox collection
}

go-ap

Collection of ActivityPub packages.

Property	Value
Repository	github.com/go-ap
License	MIT
Status	Active

Packages

• go-ap/activitypub - Core types
• go-ap/client - HTTP client
• go-ap/handlers - HTTP handlers
• go-ap/storage - Storage interface

Example

import (
    "github.com/go-ap/activitypub"
)

note := activitypub.Note{
    Type:    activitypub.NoteType,
    Content: activitypub.NaturalLanguageValues{{Value: "Hello!"}},
}

// Marshal to JSON
data, _ := json.Marshal(note)

httpsig

HTTP Signature library.

Property	Value
Repository	github.com/go-fed/httpsig
License	BSD-3
Status	Active

Signing

import "github.com/go-fed/httpsig"

signer, _ := httpsig.NewSigner(
    []httpsig.Algorithm{httpsig.RSA_SHA256},
    httpsig.DigestSha256,
    []string{httpsig.RequestTarget, "host", "date", "digest"},
    httpsig.Signature,
    0,
)

err := signer.SignRequest(privateKey, keyId, req, body)

Verification

verifier, _ := httpsig.NewVerifier(req)
pubKeyId := verifier.KeyId()

// Fetch public key using pubKeyId
err := verifier.Verify(publicKey, httpsig.RSA_SHA256)

webfinger

WebFinger client library.

Property	Value
Repository	github.com/writeas/webfinger
License	MIT
Status	Stable

Example

import "github.com/writeas/go-webfinger"

client := webfinger.NewClient(nil)

resource, err := client.Lookup("alice@example.com", nil)
if err != nil {
    log.Fatal(err)
}

// Get ActivityPub actor URL
for _, link := range resource.Links {
    if link.Rel == "self" &&
       link.Type == "application/activity+json" {
        fmt.Println(link.Href)
    }
}

GoToSocial Source

Study the GoToSocial codebase for production patterns.

Property	Value
Repository	github.com/superseriousbusiness/gotosocial
Key Paths	internal/ap/, internal/federation/

Notable Patterns

• Clean separation of concerns
• Comprehensive test coverage
• Good documentation

Comparison

Library	Scope	Complexity	Use Case
go-fed/activity	Full	High	Production servers
go-ap	Modular	Medium	Custom implementations
httpsig	Signing only	Low	Any project

Quick Start

For full servers: Use go-fed/activity.

For learning: Study GoToSocial source.

For custom needs: Use go-ap packages.

See Also

• GoToSocial
• Libraries Overview