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I'm getting started with Rust and Rocket.

I'm following the instructions with the Rocket Getting Started and I'm getting "error: Could not compile state." The full log is here:`

~/.cargo/bin/cargo run Updating registry https://github.com/rust-lang/crates.io-index Downloading rocket_codegen v0.3.3 Downloading rocket v0.3.3
Compiling gcc v0.3.54 Compiling smallvec v0.4.4 Compiling libc v0.2.34 Compiling version_check v0.1.3 Compiling language-tags v0.2.2 Compiling serde v1.0.23 Compiling state v0.3.2 error[E0554]: #![feature] may not be used on the stable release channel --> /Users/ktenjin/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:1:1 | 1 | #![feature(const_fn)] | ^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #![feature] may not be used on the stable release channel --> /Users/ktenjin/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:2:1 | 2 | #![feature(const_unsafe_cell_new)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #![feature] may not be used on the stable release channel --> /Users/ktenjin/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:3:1 | 3 | #![feature(const_atomic_usize_new)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #![feature] may not be used on the stable release channel --> /Users/ktenjin/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:4:1 | 4 | #![feature(const_atomic_bool_new)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors

error: Could not compile state. warning: build failed, waiting for other jobs to finish... error: build failed

I run it again and I got

error: Could not compile pear_codegen.

How do I resolve this. Please help! Thanks!