binding: add ShouldBindQuery2 and BindQuery2

```go
ackage main

import (
	"github.com/gin-gonic/gin"
)

type testQuery struct {
	Size int    `query:"size"`
	Page int    `query:"page"`
	Ak   string `query:"ak"`
}

func main() {
	g := gin.Default()

	g.GET("/query", func(c *gin.Context) {
		q := testQuery{}
		err := c.ShouldBindQuery2(&q)
		if err != nil {
			return
		}
		c.JSON(200, q)
	})

	g.Run()
}

// curl '127.0.0.1:8080/query?size=10&page=20&ak=test'
```

binding/binding.go

@@ -72,6 +72,7 @@ var (
 	XML           = xmlBinding{}
 	Form          = formBinding{}
 	Query         = queryBinding{}
+	Query2        = queryBinding2{}
 	FormPost      = formPostBinding{}
 	FormMultipart = formMultipartBinding{}
 	ProtoBuf      = protobufBinding{}

binding/query.go

@@ -19,3 +19,18 @@ func (queryBinding) Bind(req *http.Request, obj interface{}) error {
 	}
 	return validate(obj)
 }
+
+// Support for query tag binding data
+type queryBinding2 struct{}
+
+func (queryBinding2) Name() string {
+	return "query"
+}
+
+func (queryBinding2) Bind(req *http.Request, obj interface{}) error {
+	if err := mapFormByTag(obj, req.URL.Query(), "query"); err != nil {
+		return err
+	}
+
+	return validate(obj)
+}

context.go

@@ -572,6 +572,11 @@ func (c *Context) BindQuery(obj interface{}) error {
 	return c.MustBindWith(obj, binding.Query)
 }
 
+// BindQuery2 is a shortcut for c.MustBindWith(obj, binding.Query2).
+func (c *Context) BindQuery2(obj interface{}) error {
+	return c.MustBindWith(obj, binding.Query2)
+}
+
 // BindYAML is a shortcut for c.MustBindWith(obj, binding.YAML).
 func (c *Context) BindYAML(obj interface{}) error {
 	return c.MustBindWith(obj, binding.YAML)
@@ -631,6 +636,11 @@ func (c *Context) ShouldBindQuery(obj interface{}) error {
 	return c.ShouldBindWith(obj, binding.Query)
 }
 
+// ShouldBindQuery2 is a shortcut for c.ShouldBindWith(obj, binding.Query2).
+func (c *Context) ShouldBindQuery2(obj interface{}) error {
+	return c.ShouldBindWith(obj, binding.Query2)
+}
+
 // ShouldBindYAML is a shortcut for c.ShouldBindWith(obj, binding.YAML).
 func (c *Context) ShouldBindYAML(obj interface{}) error {
 	return c.ShouldBindWith(obj, binding.YAML)

context_test.go

@@ -1474,6 +1474,22 @@ func TestContextBindWithQuery(t *testing.T) {
 	assert.Equal(t, 0, w.Body.Len())
 }
 
+func TestContextBindWithQuery2(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	c.Request, _ = http.NewRequest("POST", "/?foo=bar&bar=foo", bytes.NewBufferString("foo=unused"))
+
+	var obj struct {
+		Foo string `query:"foo"`
+		Bar string `query:"bar"`
+	}
+
+	assert.NoError(t, c.BindQuery2(&obj))
+	assert.Equal(t, "foo", obj.Bar)
+	assert.Equal(t, "bar", obj.Foo)
+	assert.Equal(t, 0, w.Body.Len())
+}
 func TestContextBindWithYAML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)
@@ -1607,6 +1623,26 @@ func TestContextShouldBindWithQuery(t *testing.T) {
 	assert.Equal(t, 0, w.Body.Len())
 }
 
+func TestContextShouldBindWithQuery2(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	c.Request, _ = http.NewRequest("POST", "/?foo=bar&bar=foo&Foo=bar1&Bar=foo1", bytes.NewBufferString("foo=unused"))
+
+	var obj struct {
+		Foo  string `query:"foo"`
+		Bar  string `query:"bar"`
+		Foo1 string `query:"Foo"`
+		Bar1 string `query:"Bar"`
+	}
+	assert.NoError(t, c.ShouldBindQuery2(&obj))
+	assert.Equal(t, "foo", obj.Bar)
+	assert.Equal(t, "bar", obj.Foo)
+	assert.Equal(t, "foo1", obj.Bar1)
+	assert.Equal(t, "bar1", obj.Foo1)
+	assert.Equal(t, 0, w.Body.Len())
+}
+
 func TestContextShouldBindWithYAML(t *testing.T) {
 	w := httptest.NewRecorder()
 	c, _ := CreateTestContext(w)