The cpufuture in this repo is futures-cpupool 0.1.8，I vendor it here to add debug message.
cargo build --release
gdb ./target/release/demo
Then following errors will be thrown:
Got msg
Got msg done
Poll ok, NotReady
Got msg
Got msg done
Poll err:Canceled
thread 'main' panicked at /home/jiacai/grpc-rs-demo/cpufuture/src/lib.rs:332:14:
cannot poll CpuFuture twice: Canceled
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Got msg
free(): double free detected in tcache 2
Aborted
When running in debug mode, the error will be gone!