chore: Update loadgen service's Docker image to Go 1.24.

[i-adarsh]

Summary

The loadgen service in examples/instrumentation-quickstart/docker-compose.yaml fails to start because it uses the golang:1.21 image, but the command attempts to run github.com/rakyll/hey@latest. The latest version of hey (v0.1.5) requires Go 1.24 or higher.

Steps to Reproduce

1. Clone the repository: git clone https://github.com/GoogleCloudPlatform/opentelemetry-operations-java.git
2. Navigate to the example: cd opentelemetry-operations-java/examples/instrumentation-quickstart
3. Run the example: docker compose up

Expected Behavior

The loadgen container should start successfully and generate load against the application.

Actual Behavior

The loadgen container exits immediately with the following error:

loadgen-1  | go: downloading github.com/rakyll/hey v0.1.5
loadgen-1  | go: github.com/rakyll/hey@latest: github.com/rakyll/hey@v0.1.5 requires go >= 1.24.0 (running go 1.21.13; GOTOOLCHAIN=local)

This causes the entire compose stack to shut down if --abort-on-container-exit is used (as recommended in the README).

Environment

• Repository: GoogleCloudPlatform/opentelemetry-operations-java
• Path: examples/instrumentation-quickstart
• File: docker-compose.yaml
• Docker Image: golang:1.21 (Current)

Proposed Fix

Update the loadgen service in docker-compose.yaml to use a newer Go image, such as golang:1.24 or golang:latest.

[aabmass]

Maybe we should pin a version here to avoid this in the future.

@psx95 wdyt?

[psx95]

Yeah +1 to pinning the version.