chore: move the go code into a subfolder

apps/api/internal/cache/error.go

@@ -0,0 +1,29 @@
+package cache
+
+import (
+	"errors"
+	"fmt"
+)
+
+type IndexUnknownError[I comparable] struct {
+	index I
+}
+
+func NewIndexUnknownErr[I comparable](index I) error {
+	return IndexUnknownError[I]{index}
+}
+
+func (i IndexUnknownError[I]) Error() string {
+	return fmt.Sprintf("index %v unknown", i.index)
+}
+
+func (a IndexUnknownError[I]) Is(err error) bool {
+	if b, ok := err.(IndexUnknownError[I]); ok {
+		return a.index == b.index
+	}
+	return false
+}
+
+var (
+	ErrCacheMiss = errors.New("cache miss")
+)