Pretty simple, really:

go get github.com/fluffle/goirc/client

There is some example code that demonstrates usage of the library in client.go. This will connect to freenode and join #go-nuts by default, so be careful ;-)

Synopsis:

import "flag"
import irc "github.com/fluffle/goirc/client"

func main() {
    flag.Parse() // parses the logging flags.
	c := irc.SimpleClient("nick")
	// Optionally, enable SSL
	c.SSL = true

	// Add handlers to do things here!
	// e.g. join a channel on connect.
	c.AddHandler("connected",
		func(conn *irc.Conn, line *irc.Line) { conn.Join("#channel") })
	// And a signal on disconnect
	quit := make(chan bool)
	c.AddHandler("disconnected",
		func(conn *irc.Conn, line *irc.Line) { quit <- true })

	// Tell client to connect
	if err := c.Connect("irc.freenode.net"); err != nil {
		fmt.Printf("Connection error: %s\n", err.String())
	}

	// Wait for disconnect
	<-quit
}

The test client provides a good (if basic) example of how to use the framework. Reading client/handlers.go gives a more in-depth look at how handlers can be written. Commands to be sent to the server (e.g. PRIVMSG) are methods of the main *Conn struct, and can be found in client/commands.go (not all of the possible IRC commands are implemented yet). Events are produced directly from the messages from the IRC server, so you have to handle e.g. "332" for RPL_TOPIC to get the topic for a channel.

The vast majority of handlers implemented within the framework deal with state tracking of all nicks in any channels that the client is also present in. These handers are in client/state_handlers.go. State tracking is optional, disabled by default, and can be enabled and disabled by calling EnableStateTracking() and DisableStateTracking() respectively. Doing this while connected to an IRC server will probably result in an inconsistent state and a lot of warnings to STDERR ;-)

Sorry the documentation is crap. Use the source, Luke.

Feedback on design decisions is welcome. I am indebted to Matt Gruen for his work on go-bot which inspired the re-organisation and channel-based communication structure of *Conn.send() and *Conn.recv(). I'm sure things could be more asynchronous, still.

This code is (c) 2009-11 Alex Bramley, and released under the same licence terms as Go itself.