Go (`jacsgo`) Installation and Quick Start

jacsgo provides Go bindings for signing and verifying JACS documents in services, APIs, and agent runtimes.

Note: Go bindings are community-maintained. Python and Node.js currently have broader framework adapter coverage. For full MCP surface use the Rust jacs-mcp server; the Go MCP examples in the repo are demo code.

Install

go get github.com/HumanAssisted/JACS/jacsgo

Minimal Sign + Verify

Create an agent first (CLI: jacs create --name my-agent, or programmatically with jacs.Create() and JACS_PRIVATE_KEY_PASSWORD). Then:

package main

import (
	"fmt"
	"log"

	jacs "github.com/HumanAssisted/JACS/jacsgo"
)

func main() {
	// Load agent: nil = default ./jacs.config.json
	if err := jacs.Load(nil); err != nil {
		log.Fatal("create an agent first: jacs create --name my-agent")
	}

	signed, err := jacs.SignMessage(map[string]interface{}{
		"event":  "tool-result",
		"status": "ok",
	})
	if err != nil {
		log.Fatal(err)
	}

	result, err := jacs.Verify(signed.Raw)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Valid: %t signer=%s\n", result.Valid, result.SignerID)
}

Programmatic agent creation

Use jacs.Create(name, &jacs.CreateAgentOptions{...}). Password must be set in options or via JACS_PRIVATE_KEY_PASSWORD. See the jacsgo README for the full API table and options.

For multiple agents in one process, use NewJacsAgent(), then agent.Load(path) and agent methods; call agent.Close() when done. Attestation, A2A (agent cards, trust policy), and protocol helpers are available on JacsAgent and as package-level wrappers (see godoc or the jacsgo README).

Common Go Use Cases

Sign outbound API/MCP payloads before crossing trust boundaries
Verify inbound signed payloads before executing sensitive actions
Sign files (SignFile) for portable chain-of-custody workflows
Generate DNS TXT fingerprints (GetDnsRecord) for public identity verification

MCP and HTTP Patterns

The Go repository includes runnable examples for transport-level signing:

jacsgo/examples/mcp/main.go for MCP-style request/response signing
jacsgo/examples/http/ for signed HTTP client/server traffic

Identity and Trust Notes

JACS agent identity is key-based (jacsId + versioned signatures)
Verification behavior follows the configured key-resolution order in the runtime (for example local and remote resolution modes supported by the underlying JACS core)
DID interoperability is possible at the integration layer without requiring blockchain infrastructure

See DNS-Based Verification and DID Integration (No Blockchain Required).

JACS Usage Documentation