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This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: How to call async fn in a sync fn in asyn runtime

for code like this:

impl Drop for User {
    fn drop(&mut self) {
        [...]
        if self.dirty {
            self.save_when_exit();
        }
        [...]
    }
}

while save_when_exit has to be async fn because it will call sqlx;

At first, I tried

    #[tokio::main(flavor = "current_thread")]
    async fn save_when_exit(&self) {
        _ = storage::save_user_attributes(...)
        .await;
    }

But turns out it's not allowed by panic:

Cannot start a runtime from within a runtime. This happens because a function (like `block_on`) attempted to block the current thread while the thread is being used to drive asynchronous task

So, I stucked because it is impossible for drop to be a async function.
Seems there is no way out except I rename drop to some_function and calls it manually, Or spawn a new thread to execute the async function;

Both are not good, I think, because the User is created in a async fn like that

async fn xxx() {
    let u = User([...]);
    drop(u);
}

ideally, I want something like

async fn xxx() {
    let u = User([...]);
    
   // the compiler do the following impicitly
   // drop(u).await;
}

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