func (r *RocketChat) AddReceivers(channelNames ...string) {
	r.channelNames = append(r.channelNames, channelNames...)
}
AddReceivers takes rocketchat channel names and adds them to the internal channel list. The Send method will send
a given message to all channels in the list.
package rocketchat
import (
	"context"
	"net/url"
	"github.com/RocketChat/Rocket.Chat.Go.SDK/models"
	"github.com/RocketChat/Rocket.Chat.Go.SDK/rest"
	"github.com/pkg/errors"
)
type RocketChat struct {
	client       *rest.Client
	channelNames []string
}
func New(serverURL, scheme, userID, token string) (*RocketChat, error) {
	u := url.URL{
		Scheme: scheme,
		Host:   serverURL,
	}
	authInfo := models.UserCredentials{
		ID:    userID,
		Token: token,
	}
	c := rest.NewClient(&u, false)
	if err := c.Login(&authInfo); err != nil {
		return nil, err
	}
	rc := RocketChat{
		client:       c,
		channelNames: []string{},
	}
	return &rc, nil
}