Create a go-build Buildpack

[kvedurmu]

Per the Go language family re-architecture RFC we should implement a packit written go-build Buildpack that builds the go binary and writes a start command for the app.

After this change is made, ordering in the Language Family Go Buildpack should look something like

..........................................
[[order]]
  [[order.group]]
    id = "go-dist"
  [[order.group]]
    id = "go-build"

[ryanmoran]

Tasks:

• Compilation RFC: Compilation process RFC go-build#3
• Compilation RFC Implementation: Implements go build compilation process go-build#4
• Add order grouping for go-dist and go-build with integration tests: Updates paketo-buildpacks/go-build to 0.0.3 #114
• Build Flags RFC: RFC for build flags configuration go-build#5
• Build Flags RFC Implementation: Implements Build Flags RFC go-build#6

[kvedurmu]

This looks great! Verified that I can build a simple Go app (that doesn't use dep or go-mod), it detects on go-dist and go-build, has packit style log output, and app is runnable. Closing this.

pack build go-simple-app --buildpack gcr.io/paketo-buildpacks/go --verbose
..................................
Using build cache volume pack-cache-e052a863607d.build
===> DETECTING
======== Output: paketo-buildpacks/go-mod@0.0.134 ========
no "go.mod" found at: /workspace/go.mod
======== Results ========
pass: paketo-buildpacks/go-dist@0.0.178
fail: paketo-buildpacks/go-mod@0.0.134
======== Output: paketo-buildpacks/dep@0.0.146 ========
failed detection: no Gopkg.toml found at root level
======== Results ========
pass: paketo-buildpacks/go-dist@0.0.178
fail: paketo-buildpacks/dep@0.0.146
======== Results ========
pass: paketo-buildpacks/go-dist@0.0.178
pass: paketo-buildpacks/go-build@0.0.5
Resolving plan... (try #1)
paketo-buildpacks/go-dist  0.0.178
paketo-buildpacks/go-build 0.0.5
===> ANALYZING
Previous image with name "index.docker.io/library/go-simple-app:latest" not found
===> RESTORING
===> BUILDING
Go Distribution Buildpack 0.0.178
  Resolving Go version
    Candidate version sources (in priority order):
      <unknown> -> ""

    Selected Go version (using <unknown>): 1.14.4

  Executing build process
    Installing Go 1.14.4
      Completed in 22.814s
Go Build Buildpack 0.0.5
  Executing build process
    Running 'go build -o /layers/paketo-buildpacks_go-build/targets/bin -buildmode pie .'
      Completed in 1m0.976s

  Assigning launch processes
    web: /layers/paketo-buildpacks_go-build/targets/bin/workspace
===> EXPORTING
no project metadata found at path './project-metadata.toml', project metadata will not be exported
Writing tarball for layer "launcher"
Adding layer 'launcher'
Layer 'launcher' SHA: sha256:5b1dacb6040972a1132c886113abdb4e21da3f458b5d9dea09a1adea5ecb09b9
Writing tarball for layer "paketo-buildpacks/go-build:targets"
Adding layer 'paketo-buildpacks/go-build:targets'
Layer 'paketo-buildpacks/go-build:targets' SHA: sha256:eaa63a3ea0253788a165bd8b7755cf7758c1231fda27dfe57c5c95ff20c609b6
Layer 'app' SHA: sha256:79d484e29aeacbd7d4afe00dd8071ff6c4d808ecfa51f78d680b289379a3906d
Adding 1/1 app layer(s)
Writing tarball for layer "config"
Adding layer 'config'
Layer 'config' SHA: sha256:fe90ff81d22409962c8517ad42310dbf00d7518a55a84b91bdcb90b36e2da023
*** Images (51d6b7492987):
      index.docker.io/library/go-simple-app:latest

*** Image ID: 51d6b7492987a37928118dc3f48667f8f285f77162113e900a012fa379bd1ad6
Writing tarball for layer "paketo-buildpacks/go-dist:go"
Adding cache layer 'paketo-buildpacks/go-dist:go'
Layer 'paketo-buildpacks/go-dist:go' SHA: sha256:8124afca5fcf889870498ef75b0d9821a32ea367ac73aeacfcbf3e9c6f77bc2b
Writing tarball for layer "paketo-buildpacks/go-build:gocache"
Adding cache layer 'paketo-buildpacks/go-build:gocache'
Layer 'paketo-buildpacks/go-build:gocache' SHA: sha256:67586da07fcf2913d9f0d229d8e70956353085e85ae8087c9ab49255526da225
Successfully built image go-simple-app