Add log package for better logging level. (#1130)

* Add log package. Update worker with new log package.

* Add init error to worker.

* Init workers when binary launching.

* Add tests to cover different errors.

api/test_utils/env_test.go

@@ -1,26 +0,0 @@
-package test_utils
-
-import (
-	"os"
-	"strings"
-	"testing"
-)
-
-func TestPathFromAPIRoot(t *testing.T) {
-	if got, want := PathFromAPIRoot("./server.go"), "/api/server.go"; !strings.HasSuffix(got, want) {
-		t.Fatalf(`PathFromAPIRoot("./server.go") = %q, want a suffix: %q`, got, want)
-	}
-}
-
-func TestSetPathWithCurrent(t *testing.T) {
-	pathDone := SetEnv("PATH", "")
-	defer pathDone()
-
-	testDone := SetPathWithCurrent("./test")
-	defer testDone()
-
-	path := os.Getenv("PATH")
-	if got, want := path, "api/test_utils/test"; !strings.HasSuffix(got, want) {
-		t.Errorf("path = %q, want a suffix: %q", got, want)
-	}
-}