go - Schema encode failing for pointer to a slice of struct

Question

Can any one help me on encode issue for nested struct?

Go playground to reproduce the issue: playground

Getting the below issue:

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/[email protected]/encoder.go:167 +0x9d
github.com/gorilla/schema.(*Encoder).encode(0xc000010210, 0x4fb800, 0xc0000160c0, 0x99, 0xc000060270, 0xc0000160c0, 0xc000068f38)
    /tmp/gopath426458645/pkg/mod/github.com/gorilla/[email protected]/encoder.go:135 +0xa03
github.com/gorilla/schema.(*Encoder).Encode(0xc000010210, 0x4fb800, 0xc0000160c0, 0xc000060270, 0xc000068ea0, 0x40ce50)
    /tmp/gopath426458645/pkg/mod/github.com/gorilla/[email protected]/encoder.go:29 +0xb2
main.main()
    /tmp/sandbox392948750/prog.go:93 +0x548

code snippet:

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,
    }

    //encoder.RegisterEncoder(mdi.MetricDataQueries, func(reflect.Value) string { return "1" })
    form := url.Values{}
    err := encoder.Encode(mdi, form)
    if err != nil {
        fmt.Printf("Error Encode: %v
", err)
    }
    fmt.Printf("Encoded value: %v
", form)

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

}

What i see is the struct **MetricDataQueries []*MetricDataQuery schema:"MetricDataQueries.member"**is creating issue but not sure why?

question from:https://stackoverflow.com/questions/65916560/schema-encode-failing-for-pointer-to-a-slice-of-struct

Answer 1

Waitting for answers