Add support for passing in Go Build Tags to generated feature go files.

Adds support to the build and runner to pass along go build tags to the
go run command. This allows Go build tags to be triggered. Such as
`testing` build tags used for filtering in a Go project.

builder.go

@@ -15,7 +15,22 @@ const (
 	testFile         = "gucumbertest__.go"
 )
 
+// BuildAndRunDir builds the given director's features into Go Code.
+// Using the filters provided. An error is returned if the build fails.
 func BuildAndRunDir(dir string, filters []string) error {
+	return buildAndRunDir(dir, filters, "")
+}
+
+// BuildAndRunDirWithGoBuildTags builds the given director's features into Go
+// Code using the filters provided. Also takes a string for the build tags to
+// be passed to the go command. An error is returned if the build fails.
+//
+// If goBuildTags is empty, the param will be ignored.
+func BuildAndRunDirWithGoBuildTags(dir string, filters []string, goBuildTags string) error {
+	return buildAndRunDir(dir, filters, goBuildTags)
+}
+
+func buildAndRunDir(dir string, filters []string, goBuildTags string) error {
 	defer buildCleanup(dir)
 
 	info := buildInfo{
@@ -63,7 +78,12 @@ func BuildAndRunDir(dir string, filters []string) error {
 
 	// now run the command
 	tfile := "./" + filepath.ToSlash(dir) + "/_test/" + testFile
-	cmd := exec.Command("go", "run", tfile)
+	var cmd *exec.Cmd
+	if len(goBuildTags) > 0 {
+		cmd = exec.Command("go", "run", "-tags", goBuildTags, tfile)
+	} else {
+		cmd = exec.Command("go", "run", tfile)
+	}
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	if err := cmd.Run(); err != nil {

run_main.go

@@ -17,9 +17,11 @@ func (f *filters) Set(value string) error {
 }
 
 var filterFlag filters
+var goBuildTags string
 
 func init() {
 	flag.Var(&filterFlag, "tags", "comma-separated list of tags to filter scenarios by")
+	flag.StringVar(&goBuildTags, "go-tags", "", "space seperated list of tags, wrap in quotes to specify multiple tags")
 }
 
 func RunMain() {
@@ -36,7 +38,7 @@ func RunMain() {
 	for _, f := range filterFlag {
 		filt = append(filt, string(f))
 	}
-	if err := BuildAndRunDir(dir, filt); err != nil {
+	if err := BuildAndRunDirWithGoBuildTags(dir, filt, goBuildTags); err != nil {
 		panic(err)
 	}
 }