问如何从用户名中获取用户？

EN

bot.onText(/\/avvia/, (msg, match) => {   // the user must write /avvia @username
const chatId = msg.chat.id;
if(chatId != ChatGroup) { return; }   // Check if the command is executed in the right group [ChatGroup is a const with value chat.id]

if(match.input == '/avvia')           // Check if it's just typing the command
{
    bot.sendMessage(chatId, 'Only /avvia');
    return;
}

var aCaso = match.input.replace('/avvia ', '').split(' ');
const resp = aCaso[0];

bot.getChatMember(chatId, resp /* <= THIS ONE*/).then( response => { // Check if the forwarded user is in the group
    //console.log(response)                                          // But RESP is wrong because is 
    if(response.status == 'left' || response.status == 'kicked')     // getChatMember(string|int chatId, int userId), and not a username
    {
        bot.sendMessage(chatId, 'Not in the group');
        return
    }
})

//console.log(resp);
});