$ go get github.com/nlopes/slack

import (
	"fmt"

	"github.com/nlopes/slack"
)

func main() {
	api := slack.New("YOUR_TOKEN_HERE")
	// If you set debugging, it will log all requests to the console
	// Useful when encountering issues
	// api.SetDebug(true)
	groups, err := api.GetGroups(false)
	if err != nil {
		fmt.Printf("%s\n", err)
		return
	}
	for _, group := range groups {
		fmt.Printf("ID: %s, Name: %s\n", group.ID, group.Name)
	}
}

import (
    "fmt"

    "github.com/nlopes/slack"
)

func main() {
    api := slack.New("YOUR_TOKEN_HERE")
    user, err := api.GetUserInfo("U023BECGF")
    if err != nil {
	    fmt.Printf("%s\n", err)
	    return
    }
    fmt.Printf("ID: %s, Fullname: %s, Email: %s\n", user.ID, user.Profile.RealName, user.Profile.Email)
}