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Rust errors / Build and Cargo

Rust build error · checked with Rust 1.99.0

error[E0752]: `main` function is not allowed to be `async`

error[E0752]: `main` function is not allowed to be `async`

What it meansRust has no built-in async runtime, so main cannot be async on its own. A runtime macro like tokio::main turns it into a normal main that runs your async code.

Why it happens

  • Writing async fn main() without a runtime attribute.
  • tokio added without the macros and rt-multi-thread features.

How to fix it

1. Use tokio's main macro

cargo add tokio --features full

#[tokio::main]
async fn main() {
    // async code here
}

Other wordings of this error

main function is not allowed to be async, async fn main not allowed, E0752

Other build errors

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