where to add synchronize

foo.d

import std;
import core.thread;
import core.time;

class Foo
{
    shared string[int] bucket;
    
    Tid worker;
    
    auto getStringFromWorker()
    {
        int i = uniform(1, int.max);
        bucket[i] = string.init;  // key assumed unique for brevity
        
        const timestampBefore = Clock.currTime;
        enum maxWait = 5.seconds;
        worker.send(i);
        
        while ((Clock.currTime - timestampBefore) < maxWait)
        {
            auto inBucket = i in bucket;
                
            if (inBucket && (inBucket.length > 0))
            {
                string s = *inBucket;
                bucket.remove(i);
                return s;
            }
            else
            {
                // Value non-existent or still empty
                Thread.sleep(100.msecs);
            }
        }
        
        return null;
    }
}

void main()
{
    auto foo = new Foo;
    foo.bucket[0] = string.init;
    foo.bucket.remove(0);
    foo.worker = spawn(&workerFn, foo.bucket);
    
    foreach (i; 0..10)
    {
        writeln("string from worker:", foo.getStringFromWorker());
    }
}

void workerFn(shared string[int] bucket)
{
    bool halt;

    while (!halt)
    {
        receive(
            (int i)
            {
                //writeln("worker received request to assign value to bucket key ", i);
                Thread.sleep(150.msecs);  // simulate workload
                bucket[i] = i.to!string;
            },
            (OwnerTerminated _)
            {
                halt = true;
            }
        );
    }
}