Implement blackbox in Golang (#250)

* Initial release

pkg/crypters/crypters.go

@@ -0,0 +1,58 @@
+package crypters
+
+import (
+	"sort"
+	"strings"
+
+	"github.com/StackExchange/blackbox/v2/models"
+)
+
+// Crypter is the handle
+type Crypter interface {
+	models.Crypter
+}
+
+// NewFnSig function signature needed by reg.
+type NewFnSig func(debug bool) (Crypter, error)
+
+// Item stores one item
+type Item struct {
+	Name     string
+	New      NewFnSig
+	Priority int
+}
+
+// Catalog is the list of registered vcs's.
+var Catalog []*Item
+
+// SearchByName returns a Crypter handle for name.
+// The search is case insensitive.
+func SearchByName(name string, debug bool) Crypter {
+	name = strings.ToLower(name)
+	for _, v := range Catalog {
+		//fmt.Printf("Trying %v %v\n", v.Name)
+		if strings.ToLower(v.Name) == name {
+			chandle, err := v.New(debug)
+			if err != nil {
+				return nil // No idea how that would happen.
+			}
+			//fmt.Printf("USING! %v\n", v.Name)
+			return chandle
+		}
+	}
+	return nil
+}
+
+// Register a new VCS.
+func Register(name string, priority int, newfn NewFnSig) {
+	//fmt.Printf("CRYPTER registered: %v\n", name)
+	item := &Item{
+		Name:     name,
+		New:      newfn,
+		Priority: priority,
+	}
+	Catalog = append(Catalog, item)
+
+	// Keep the list sorted.
+	sort.Slice(Catalog, func(i, j int) bool { return Catalog[j].Priority < Catalog[i].Priority })
+}