Worker is not finished while sending message to intermediate worker

[xtreak via Digitalmars-d-learn]

I am using "programming in D" to learn about D language. I wrote 
a simple program that spawns a worker and sends it a number to 
receive its square as a string. The worker 1 gets the number 
squares it and sends to worker 2 (a different function) to get 
casted as string which is returned to the worker 1 and thus it 
returns it to the main function call. I can write the whole thing 
in a single thread. I wrote it to understand about workers 
better. I used receive to get the worker 1 act as per the input. 
The program is as follows

import std.stdio;
import std.concurrency;
import std.conv;
import core.thread;

void main() {

   foreach (int num; 1..100) {
     auto square_tid = spawn(&square);
     square_tid.send(num);
     auto square = receiveOnly!string();
     writeln(square);
   }
}


void square() {
   static i = 0;
   receive (
        (int num) {
          auto square = num * num;
          writeln("sqaure : Comes in with " , num , " for " , ++i 
, " time");
          auto stringWorker = spawn(&stringConverter);
          stringWorker.send(thisTid, square, ownerTid);
        },
        (Tid tid, string str) {
          writeln("comes in string");
          send(tid, "hello");
        });
}

void stringConverter() {
   static i = 0;
   auto params = receiveOnly!(Tid, int, Tid)();
   auto stringified = to!string(params[1]); // Stringify the square
   writeln("string : Comes in with " , params[1], " for " , ++i , 
" time");
   params[0].send(params[2], stringified); // params[0] - square 
function tid, // params[2] - main function tid
}


I got the answer from stackoverflow @ 
https://stackoverflow.com/questions/28128383/worker-is-not-finished-while-sending-message-to-intermediate-worker. 
But the person who answered my question asked me to post back to 
dlang learn to learn more about it. As I spawn the function and a 
send a message to stringConverter as it sends a message to the 
square function why do I need to embed another receive call 
inside the int case as indicated in the answer. How can I avoid 
embedding the receive call and why does the person in the second 
answer used while(1) to receive the message.