@Nullable
    public static CoroutineContext get(RequestContext ctx) {
        requireNonNull(ctx, "ctx");
        return ctx.attr(COROUTINE_CONTEXT_KEY);
    }
Returns the coroutine context mapped to {@code COROUTINE_CONTEXT_KEY} in the context.
kotlin/src/main/java/com/linecorp/armeria/common/kotlin/CoroutineContexts.java