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

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

internal/cache/cache_test.go

@@ -0,0 +1,21 @@
+package cache
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_SetManager(t *testing.T) {
+	original := GetManager()
+	defer SetManager(original)
+
+	SetManager(NewInMemory(0))
+
+	require.NotNil(t, GetManager())
+	require.IsType(t, &filesystemCache{}, GetManager())
+
+	SetManager(nil)
+	require.NotNil(t, GetManager())
+	require.IsType(t, &bypassedCache{}, GetManager())
+}