Struct ScopedJoinHandle 

pub struct ScopedJoinHandle<'scope, R> { /* private fields */ }

A handle to a goroutine spawned inside a Scope.

Call join to park the current goroutine until the scoped goroutine finishes and retrieve its result.

Dropping the handle without joining is safe — the goroutine still runs to completion (the enclosing scope guarantees this). Any return value or panic from an un-joined goroutine is silently discarded.

Why join returns Result instead of the value directly

go-lib goroutines are M:N scheduled; they can migrate between OS threads. Rust’s resume_unwind depends on C++ EH machinery that is bound to the OS thread on which catch_unwind was called. Calling resume_unwind after a goroutine has parked and been rescheduled on a different thread bypasses the inner landing pad and produces undefined behaviour. Returning std::thread::Result<R> lets the caller choose what to do — typically .unwrap() or matching on the payload — without crossing any scheduling boundary.

Implementations

impl<'scope, R: Send + 'static> ScopedJoinHandle<'scope, R>

pub fn join(self) -> Result<R>

Park the current goroutine until the scoped goroutine finishes.

Returns Ok(value) if the goroutine returned normally, or Err(panic_payload) if it panicked.

To propagate the panic as-is call std::panic::resume_unwind(err) from outside any goroutine scheduling boundary — i.e., directly in the scope closure without any intervening channel/wait operations. For the common case, .unwrap() is usually simpler.