fix: separate golang license caches from mod dir (#2852)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

internal/cache/memory.go

@@ -0,0 +1,16 @@
+package cache
+
+import (
+	"time"
+
+	"github.com/spf13/afero"
+)
+
+// NewInMemory returns an in-memory only cache manager
+func NewInMemory(ttl time.Duration) Manager {
+	return &filesystemCache{
+		dir: "",
+		fs:  afero.NewMemMapFs(),
+		ttl: ttl,
+	}
+}