Return only alpha numeric characters as an ID

On some providers the default character set used by shortid may lead to
errors when creating runners, due to the fact that underscores are not
allowed in their names.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

runner/pool/pool.go

@@ -33,9 +33,7 @@ import (
 	"garm/util"
 
 	"github.com/google/go-github/v48/github"
-	"github.com/google/uuid"
 	"github.com/pkg/errors"
-	"github.com/teris-io/shortid"
 )
 
 var (
@@ -396,11 +394,7 @@ func (r *basePoolManager) AddRunner(ctx context.Context, poolID string) error {
 		return errors.Wrap(err, "fetching pool")
 	}
 
-	suffix, err := shortid.Generate()
-	if err != nil {
-		suffix = uuid.New().String()
-	}
-	name := fmt.Sprintf("%s-%s", pool.GetRunnerPrefix(), suffix)
+	name := fmt.Sprintf("%s-%s", pool.GetRunnerPrefix(), util.NewID())
 
 	createParams := params.CreateInstanceParams{
 		Name:          name,

util/util.go

@@ -38,8 +38,10 @@ import (
 	"garm/runner/common"
 
 	"github.com/google/go-github/v48/github"
+	"github.com/google/uuid"
 	gorillaHandlers "github.com/gorilla/handlers"
 	"github.com/pkg/errors"
+	"github.com/teris-io/shortid"
 	"golang.org/x/crypto/bcrypt"
 	"golang.org/x/oauth2"
 	lumberjack "gopkg.in/natefinch/lumberjack.v2"
@@ -331,3 +333,27 @@ func NewLoggingMiddleware(writer io.Writer) func(http.Handler) http.Handler {
 func SanitizeLogEntry(entry string) string {
 	return strings.Replace(strings.Replace(entry, "\n", "", -1), "\r", "", -1)
 }
+
+func randomCharacter() string {
+	for i := 0; i < 5; i++ {
+		character, err := GetRandomString(1)
+		if err != nil {
+			continue
+		}
+		return character
+	}
+	return ""
+}
+
+func NewID() string {
+	newID, err := shortid.Generate()
+	if err != nil {
+		newID = uuid.New().String()
+	} else {
+		// remove underscores and hyphens from short ID. The hypens will remain
+		// if we are forced to fall back to uuid4.
+		newID = strings.Replace(newID, "_", randomCharacter(), -1)
+		newID = strings.Replace(newID, "-", randomCharacter(), -1)
+	}
+	return newID
+}