Hi, 

import std.stdio;
import vibe.core.core;
import vibe.core.concurrency;


class Result
{
 	int value = 42;
}

Result process()
{
 	return new Result();
}

void main()
{
    auto res = async({
    	return process();
    });    
    
    writeln(res.getResult());
}

https://run.dlang.io/is/BYPkIg

.dub/packages/vibe-core-1.4.3/vibe-core/source/vibe/core/concurrency.d(1146,3): Error: inout method vibe.internal.freelistref.FreeListRef!(shared(Result), true).FreeListRef.get is not callable using a mutable object
onlineapp.d(22,21): Error: template instance vibe.core.concurrency.async!(Result function() @system) error instantiating
.dub/packages/vibe-core-1.4.3/vibe-core/source/vibe/core/concurrency.d(1105,32): Error: this.m_result.get() is not an lvalue and cannot be modified
dmd failed with exit code 1.

I don't understand what I'm missing ?

Thanks