/+ dub.sdl:
 
name "app"
dependency "mylib" path="./mylib"
+/
 
import std.exception: enforce;
import std.file: exists, thisExePath;
import std.path: dirName, buildPath;
 
void main()
{
    string filePath = buildPath(thisExePath.dirName, "helloworld.txt");
    enforce(filePath.exists);
}