[bug] Golang gorilla schema encode failing for pointer to a slice of struct

[sahajavidya]

Describe the bug

A clear and concise description of what the bug is.

Golang gorilla schema encode failing for pointer to a slice of struct
…

Versions

Go version: go version -- go version go1.14
package version: run git rev-parse HEAD inside the repo

…

Steps to Reproduce

How can the bug be triggered?

…
go playground

Expected behavior

What output or behaviour were you expecting instead?
Should not crash with error -
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4d661d]

goroutine 1 [running]:
github.com/gorilla/schema.typeEncoder.func1(0x4e0de0, 0xc00000e028, 0x196, 0x0, 0x4e0de0)
/tmp/gopath426458645/pkg/mod/github.com/gorilla/schema@v1.2.0/encoder.go:167 +0x9d
github.com/gorilla/schema.(*Encoder).encode(0xc000010210, 0x4fb800, 0xc0000160c0, 0x99, 0xc000060270, 0xc0000160c0, 0xc000068f38)
/tmp/gopath426458645/pkg/mod/github.com/gorilla/schema@v1.2.0/encoder.go:135 +0xa03
github.com/gorilla/schema.(*Encoder).Encode(0xc000010210, 0x4fb800, 0xc0000160c0, 0xc000060270, 0xc000068ea0, 0x40ce50)
/tmp/gopath426458645/pkg/mod/github.com/gorilla/schema@v1.2.0/encoder.go:29 +0xb2
main.main()
/tmp/sandbox392948750/prog.go:93 +0x548

…

Code Snippets

A minimum viable code snippet can be useful! (use backticks to format it).

package main

import (
	"fmt"
	"net/url"
	"time"

	"github.com/gorilla/schema"
)

var (
	encoder = schema.NewEncoder()
)

type GetMetricDataInput struct {
	EndTime           *time.Time         `schema:"EndTime"`
	MaxDatapoints     *int64             `schema:"MaxDatapoints"`
	MetricDataQueries []*MetricDataQuery `schema:"MetricDataQueries.member"`
	NextToken         *string            `schema:"NextToken"`
	ScanBy            *string            `schema:"ScanBy"`
	StartTime         *time.Time         `schema:"StartTime"`
}

type MetricDataQuery struct {
	Id         *string
	Label      *string
	MetricStat *MetricStat
	Period     *int64
	ReturnData *bool
}

type MetricStat struct {
	Metric *Metric
	Period *int64
	Stat   *string
}

type Metric struct {
	Dimensions []*Dimension
	MetricName *string
	Namespace  *string
}

type Dimension struct {
	Name  *string
	Value *string
}

func main() {

	endTime := time.Now()
	var maxDatapoints int64 = 1
	id := "id"
	label := "label"
	instanceID := "InstanceId"
	val := "i-09603b2a8a61d831f"
	metricName := "CPUUtilization"
	namespace := "AWS/EC2"
	var period int64 = 60
	stat := "Minimum"
	returnData := true
	scanby := "scanby"
	startTime := time.Now()

	mdi := GetMetricDataInput{
		EndTime:       &endTime,
		MaxDatapoints: &maxDatapoints,
		MetricDataQueries: []*MetricDataQuery{{
			Id:    &id,
			Label: &label,
			MetricStat: &MetricStat{
				Metric: &Metric{
					Dimensions: []*Dimension{{
						Name:  &instanceID,
						Value: &val,
					}},
					MetricName: &metricName,
					Namespace:  &namespace,
				},
				Period: &period,
				Stat:   &stat,
			},
			Period:     &period,
			ReturnData: &returnData,
		}},
		NextToken: nil,
		ScanBy:    &scanby,
		StartTime: &startTime,
	}

	form := url.Values{}
	err := encoder.Encode(mdi, form)
	if err != nil {
		fmt.Printf("Error Encode: %v\n", err)
	}
	fmt.Printf("Encoded value: %v\n", form)

	res := form.Encode()
	fmt.Printf("Resonse: %v\n", res)

}

…

[stale]

This issue has been automatically marked as stale because it hasn't seen a recent update. It'll be automatically closed in a few days.