feat: add prometheus metrics without external standalone exporter

models/metrics/label.go

@@ -0,0 +1,28 @@
+package metrics
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Labels []Label
+
+type Label struct {
+	Key   string
+	Value string
+}
+
+func (l Labels) Print() string {
+	printedLabels := make([]string, len(l))
+	for i, e := range l {
+		printedLabels[i] = e.Print()
+	}
+	if len(l) == 0 {
+		return ""
+	}
+	return fmt.Sprintf("{%s}", strings.Join(printedLabels, ","))
+}
+
+func (l Label) Print() string {
+	return fmt.Sprintf("%s=\"%s\"", l.Key, l.Value)
+}