Merge pull request #34491: Adds instructions regarding building the Go SDK harness container for Dataflow

Author: chamikaramj

contributor-docs/code-change-guide.md

@@ -37,6 +37,8 @@ The guide contains the following sections:
   for Python development, running unit and integration tests, and running a pipeline
   with modified Beam code.
 
+For instructions regarding testing code changes for Go SDK, please see the Go SDK's [README file](https://github.com/apache/beam/tree/master/sdks/go).
+
 ## Repository structure
 
 The Apache Beam GitHub repository (Beam repo) is, for the most part, a "mono repo".

sdks/go/README.md

@@ -106,8 +106,19 @@ sport: 3
 Crown'd: 1
 ```
 
+Note that, when running at Beam HEAD, the Dataflow runner will try to use a non-existent container `gcr.io/cloud-dataflow/v1beta3/beam_go_sdk:<Beam version>.dev`.
+To address this, you need to push your own SDK harness container image to a repository (for example, Docker Hub or Google Artifact Registry) and specify that as the
+`<YOUR_SDK_HARNESS_IMAGE_LOCATION>` parameter above.
+For example, running the following from Beam HEAD, will make the container availble at the location `<repository>/beam_go_sdk`.
+
+```bash
+$ ./gradlew :sdks:go:container:docker -Pdocker-repository-root=<repository>
+
+$ docker push <repository>/beam_go_sdk
+```
+
 See [BUILD.md](./BUILD.md) for how to build Go code in general. See
-[container documentation](https://beam.apache.org/documentation/runtime/environments/#building-container-images) for how to build and push the Go SDK harness container image.
+[container documentation](https://beam.apache.org/documentation/runtime/environments/#building-container-images) for more details on how to build and push the Go SDK harness container image.
 
 ## Issues