use golang-builder like other concourse resources now do

[dandersonsw]

Changes proposed in this pull request:

• Updates the dockerfile to use the golang-builder image to actually compile the commands. Concourse switched to this method for the resource repos, but this one was never updated to follow this new method

Things to check

• For any logging statements, is there any chance that they could be logging sensitive data?
• Are log statements using a logging library with a logging level set? Setting a logging level means that log statements "below" that level will not be written to the output. For example, if the logging level is set to INFO and debugging statements are written with log.debug or similar, then they won't be written to the otput, which can prevent unintentional leaks of sensitive data.

Security considerations

Setting up the code to properly compile

[JasonTheMain]

Looks good