add test for struct parameter to async function being copied
add test for struct parameter to async function being copied

closes #1155

zig-lang/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,andrewrk/zig