Add -parser flag to choose which parser to use

The two parsers that are supported are `gotest` (default), and `gojson`.
They handle the standard `go test -v` and `go test -json` output
respectively.

go-junit-report.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/jstemmer/go-junit-report/v2/pkg/gtr"
 	"github.com/jstemmer/go-junit-report/v2/pkg/junit"
 	"github.com/jstemmer/go-junit-report/v2/pkg/parser/gotest"
 )
@@ -28,6 +29,7 @@ var (
 	output      = flag.String("out", "", "write XML report to `file`")
 	iocopy      = flag.Bool("iocopy", false, "copy input to stdout; can only be used in conjunction with -out")
 	properties  = make(keyValueFlag)
+	inputParser = flag.String("parser", "gotest", "set input parser: gotest, gojson")
 
 	// debug flags
 	printEvents = flag.Bool("debug.print-events", false, "print events generated by the go test parser")
@@ -75,7 +77,17 @@ func main() {
 		in = io.TeeReader(in, os.Stdout)
 	}
 
-	parser := gotest.New(gotest.PackageName(*packageName))
+	var parser Parser
+	switch *inputParser {
+	case "gotest":
+		parser = gotest.New(gotest.PackageName(*packageName))
+	case "gojson":
+		parser = gotest.NewJSON(gotest.PackageName(*packageName))
+	default:
+		fmt.Fprintf(os.Stderr, "invalid parser: %s\n", *inputParser)
+		flag.Usage()
+		os.Exit(1)
+	}
 
 	report, err := parser.Parse(in)
 	if err != nil {
@@ -166,3 +178,8 @@ func (f *keyValueFlag) Set(value string) error {
 	(*f)[k] = v
 	return nil
 }
+
+type Parser interface {
+	Parse(r io.Reader) (gtr.Report, error)
+	Events() []gotest.Event
+}