Fix Dockerfile in try/4.0/docker-stack.md

[Terkwood]

Change Request

The Dockerfile used to build the client example app in https://tikv.org/docs/4.0/tasks/try/docker-stack/ does not work.

Describe the problem

non-interactive install for tzdata

I used DEBIAN_FRONTEND="noninteractive", so that tzdata would not prompt during installation. I also had to use apt-get instead of apt!

RUN DEBIAN_FRONTEND="noninteractive" apt-get install --yes build-essential protobuf-compiler curl cmake golang libssl-dev

rust stable has async await

The doc website incorrectly requires a nightly rust toolchain. This is no longer necessary since async/await functionality has landed in rust stable. I removed all references to the version-hacking file rust-toolchain.

# ...snip...
# Install Rust
RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
ENV PATH="/builder/.cargo/bin:${PATH}"

# Fetch, then prebuild all deps
COPY Cargo.toml /builder/build/

Missing libssl-dev

I also had to install libssl-dev.

RUN DEBIAN_FRONTEND="noninteractive" apt-get install --yes build-essential protobuf-compiler curl cmake golang libssl-dev

Suggest an improvement/fix

I will raise a PR presently to address this issue.

Thank you for taking the time to review this request!