[GO] Fix value formatting in url with slices (#15581)

* fix reflect value for Slice

* Add test

Author: darkrift

modules/openapi-generator/src/main/resources/go/api.mustache

@@ -189,7 +189,7 @@ func (a *{{{classname}}}Service) {{nickname}}Execute(r {{#structPrefix}}{{&class
 		if reflect.TypeOf(t).Kind() == reflect.Slice {
 			s := reflect.ValueOf(t)
 			for i := 0; i < s.Len(); i++ {
-				parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", s.Index(i), "{{collectionFormat}}")
+				parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", s.Index(i).Interface(), "{{collectionFormat}}")
 			}
 		} else {
 			parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", t, "{{collectionFormat}}")
@@ -207,7 +207,7 @@ func (a *{{{classname}}}Service) {{nickname}}Execute(r {{#structPrefix}}{{&class
 		if reflect.TypeOf(t).Kind() == reflect.Slice {
 			s := reflect.ValueOf(t)
 			for i := 0; i < s.Len(); i++ {
-				parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", s.Index(i), "{{collectionFormat}}")
+				parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", s.Index(i).Interface(), "{{collectionFormat}}")
 			}
 		} else {
 			parameterAddToHeaderOrQuery(localVarQueryParams, "{{baseName}}", t, "{{collectionFormat}}")

samples/client/petstore/go/go-petstore/api_fake.go

@@ -9,7 +9,8 @@ import (
 )
 
 const (
-	deepObjectURL = `/v2/fake/deep_object_test?inputOptions[F1]=1&inputOptions[F2]=teststring&inputOptions[F3]=null&inputOptions[id]=1&inputOptions[name]=TestCat&test_pet[F1]=1&test_pet[F2]=teststring&test_pet[F3]=null&test_pet[id]=1&test_pet[name]=Test&test_pet[photoUrls]=http%3A%2F%2Flocalhost&test_pet[tags][F1]=1&test_pet[tags][F2]=teststring&test_pet[tags][F3]=null&test_pet[tags][id]=2&test_pet[tags][name]=tag1`
+	deepObjectURL            = `/v2/fake/deep_object_test?inputOptions[F1]=1&inputOptions[F2]=teststring&inputOptions[F3]=null&inputOptions[id]=1&inputOptions[name]=TestCat&test_pet[F1]=1&test_pet[F2]=teststring&test_pet[F3]=null&test_pet[id]=1&test_pet[name]=Test&test_pet[photoUrls]=http%3A%2F%2Flocalhost&test_pet[tags][F1]=1&test_pet[tags][F2]=teststring&test_pet[tags][F3]=null&test_pet[tags][id]=2&test_pet[tags][name]=tag1`
+	paramCollectionFormatURL = `/v2/fake/test-query-parameters?context=context&http=http&ioutil=ioutil&pipe=pipe&url=url`
 )
 
 // TestPutBodyWithFileSchema ensures a model with the name 'File'
@@ -39,12 +40,12 @@ func TestQueryDeepObject(t *testing.T) {
 	var idTag1 = int64(2)
 	var nameTag1 = "tag1"
 	req = req.TestPet(sw.Pet{
-		Id: &id,
-		Name: "Test",
-		PhotoUrls: []string{ "http://localhost" },
+		Id:        &id,
+		Name:      "Test",
+		PhotoUrls: []string{"http://localhost"},
 		Tags: []sw.Tag{
 			{
-				Id: &idTag1,
+				Id:   &idTag1,
 				Name: &nameTag1,
 				AdditionalProperties: map[string]interface{}{
 					"F1": 1,
@@ -61,7 +62,7 @@ func TestQueryDeepObject(t *testing.T) {
 	})
 	var idcat = int64(1)
 	req = req.InputOptions(sw.Category{
-		Id: &idcat,
+		Id:   &idcat,
 		Name: "TestCat",
 		AdditionalProperties: map[string]interface{}{
 			"F1": 1,
@@ -76,5 +77,22 @@ func TestQueryDeepObject(t *testing.T) {
 
 	assert.Equal(t,
 		expectedDeepObjectURL,
-		r.Request.URL.String() )
+		r.Request.URL.String())
+}
+
+func TestQueryParameterCollectionFormat(t *testing.T) {
+	req := client.FakeAPI.TestQueryParameterCollectionFormat(context.Background()).
+		Pipe([]string{"pipe"}).
+		Ioutil([]string{"ioutil"}).
+		Http([]string{"http"}).
+		Url([]string{"url"}).
+		Context([]string{"context"})
+
+	r, _ := req.Execute()
+
+	var expectedParamCollectionFormatURL = testScheme + "://" + testHost + paramCollectionFormatURL
+
+	assert.Equal(t,
+		expectedParamCollectionFormatURL,
+		r.Request.URL.String())
 }