test: add example test

example_key_test.go

@@ -0,0 +1,36 @@
+package query_test
+
+import (
+	"fmt"
+
+	"github.com/zoncoen/query-go"
+)
+
+type orderedMap struct {
+	elems []*elem
+}
+
+type elem struct {
+	k, v interface{}
+}
+
+func (m *orderedMap) ExtractByKey(key string) (interface{}, bool) {
+	for _, e := range m.elems {
+		if k, ok := e.k.(string); ok {
+			if k == key {
+				return e.v, true
+			}
+		}
+	}
+	return nil, false
+}
+
+func ExampleKeyExtractor() {
+	q := query.New().Key("key")
+	v, _ := q.Extract(&orderedMap{
+		elems: []*elem{{k: "key", v: "value"}},
+	})
+	fmt.Println(v)
+	// Output:
+	// value
+}