问如何在Ballerina中通过菜单驱动的应用程序调用服务

EN

function main(string... args) {
    int c = 0;
    while ( c != 2) {
        // print options menu to choose from
        io:println("-------------------------------------------------------------------------");
        io:println("1. Email");
        io:println("2. Exit");
        io:println("-------------------------------------------------------------------------");
        // read user's choice
        string choice = io:readln("Enter choice 1 - 2: ");
        c = check <int>choice;

        if (c == 1) {
           //code to send email            
        }

        if (c == 2) {
            break;
        } 
    }     
}

// A system package containing protocol access constructs
// Package objects referenced with 'http:' in code
import ballerina/http;
import ballerina/io;
import wso2/gmail;
import ballerina/config;

endpoint gmail:Client gmailEP {
    clientConfig:{
        auth:{
            accessToken:config:getAsString("accessToken"),
            clientId:config:getAsString("clientId"),
            clientSecret:config:getAsString("clientSecret"),
            refreshToken:config:getAsString("refreshToken")
        }
    }
};

documentation {
   A service endpoint represents a listener.
}
endpoint http:Listener listener {
    port:9090
};

documentation {
   A service is a network-accessible API
   Advertised on '/hello', port comes from listener endpoint
}

@http:ServiceConfig {
   basePath: "/"
}

service<http:Service> hello bind listener {
    @http:ResourceConfig {
        methods: ["POST"],
        path: "/"
    }

    documentation {
       A resource is an invokable API method
       Accessible at '/hello/sayHello
       'caller' is the client invoking this resource 

       P{{caller}} Server Connector
       P{{request}} Request
    }

    sayHello (endpoint caller, http:Request request) {
        gmail:MessageRequest messageRequest;
        messageRequest.recipient = "abc@gmail.com";
        messageRequest.sender = "efg@gmail.com";
        messageRequest.cc = "";
        messageRequest.subject = "Email-Subject";
        messageRequest.messageBody = "Email Message Body Text";
        //Set the content type of the mail as TEXT_PLAIN or TEXT_HTML.
       messageRequest.contentType = gmail:TEXT_PLAIN;
        //Send the message.
        var sendMessageResponse = gmailEP -> sendMessage("efg@gmail.com", messageRequest); 
    }

}