Can't use icons

[joseooortega]

I tried to send icon with slack message but i can't get it done.

As the readme shows, I tried the following:

slack.send({
    text: `${environment} - ${finalMessage}`,
    channel: `#${channel}`,
    username: 'Bot',
    icon_emoji: ':taco:',
});

May I have to put :taco: in the message body? If i do that it works but then why i have to use 'icon_emoji' property?

Thank you in advance.