Can you try replacing the @safe with @trusted for the authenticate
method above? The API in vibe.d 0.7.x is not yet annotated with @safe,
so the compiler will complain when it is called from an @safe context.

Alternatively, you could try upgrading to 0.8.0, which is fully @safe,
but that could lead to warnings in other areas of your because not all
code is @safe. In the long run, this is definitely the way to go,
though, since memory safety is so critical for public server applications.

Thank you for reply. For test purposes i removed @safe from function and it starts working. Second "solution" - forcing upgrade to newer version - solved it too. Thank you for help. Now it is working as i expected.