Stub out go binary build and tests (#649)

* Stub out go binary build and tests

.travis.yml

-language: bash
+language: go
+go:
+  - "1.12"
 sudo: required
 services:
   - docker
@@ -9,6 +11,7 @@ env:
   - TEST=cedar-14 STACK=cedar-14
   - TEST=hatchet
   - TEST=unit
+  - TEST=test-binary GO111MODULE=on
 install:
   - if [[ -n $STACK ]]; then
       docker pull "heroku/${STACK/-/:}";

cmd/resolve-version/main.go

+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("hello world")
+}

cmd/resolve-version/main_test.go

+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseObject(t *testing.T) {
+	assert.Equal(t, 0, 0)
+}

go.mod

+module github.com/heroku/heroku-buildpack-nodejs
+
+go 1.12
+
+require github.com/stretchr/testify v1.3.0

go.sum

+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=

makefile

 test: heroku-18 heroku-16 cedar-14
 
+build:
+	@GOOS=darwin GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-darwin ./cmd/resolve-version
+	@GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-linux ./cmd/resolve-version
+
+test-binary:
+	go test -v ./cmd/...
+
 shellcheck:
 	@shellcheck -x bin/compile bin/detect bin/release bin/test bin/test-compile
 	@shellcheck -x lib/**