ecs-gpu-init: Upgrade Go module go directive to 1.18

[jpmcb]

Issue number:

Related: #2420

Description of changes:

This upgrades the Go build directive in the go module for ecs-gpu-init to reflect the version we use in the SDK. Should be a very low risk change and Go 1.16 has been out of support for awhile now

Testing done:

Able to build Go the code: go build ./cmd/ecs-gpu-init 👍🏼
Able to build the package: cargo make -e PACKAGE=ecs-gpu-init pacakge 👍🏼

Not sure if this requires more extensive testing since it builds ok

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[arnaldo2792]

Could you please make sure ECS tasks that require GPUs are still working? 😄

[jpmcb]

Built an nvidia variant AMI and started a p2.xlarge GPU instance for my ECS cluster.

Then, on inspecting the nvidia-gpu-info.json file on the host 👍🏼

bash-5.1# cat /var/lib/ecs/gpu/nvidia-gpu-info.json
{"DriverVersion":"470.82.01","GPUIDs":["<GPU-ID>"]}
bash-5.1#