how to build and test with docker (#61)

* how to build and test with docker

* typo

Author: softprops

README.md

@@ -128,6 +128,40 @@ Invoke it using serverless framework or a configured AWS integrated trigger sour
 $ npx serverless invoke -f hello -d '{"foo":"bar"}'
 ```
 
+#### Docker
+
+Alternatively, you can build a Rust-based Lambda function in a [docker mirror of the AWS Lambda provided runtime with the Rust toolchain preinstalled](https://github.com/softprops/lambda-rust).
+
+Running the following command will start a emphemeral docker container which will build your Rust application and produce a zip file containing its binary auto-renamed to `bootstrap` to meet the AWS Lambda's expectations for binaries under `target/lambda/release/{your-binary-name}.zip`, typically this is just the name of your crate if you are using the cargo default binary (i.e. `main.rs`)
+
+```bash
+# build and package deploy-ready artifact
+$ docker run --rm \
+    -v ${PWD}:/code \
+    -v ${HOME}/.cargo/registry:/root/.cargo/registry \
+    -v ${HOME}/.cargo/git:/root/.cargo/git \
+    softprops/lambda-rust
+```
+
+With your application build and packaged, it's ready to ship to production. You can also invoke it locally to verify is behavior using the [lambdaci :provided docker container](https://hub.docker.com/r/lambci/lambda/) which is also a mirror of the AWS Lambda provided runtime with build dependencies omitted.
+
+```bash
+# start a docker container replicating the "provided" lambda runtime
+# awaiting an event to be provided via stdin
+$ unzip -o \
+    target/lambda/release/{your-binary-name}.zip \
+    -d /tmp/lambda && \
+  docker run \
+    -i -e DOCKER_LAMBDA_USE_STDIN=1 \
+    --rm \
+    -v /tmp/lambda:/var/task \
+    lambci/lambda:provided
+
+# provide an event payload via stdin (typically a json blob)
+
+# Ctrl-D to yield control back to your function
+```
+
 
 ## lambda-runtime-client