Handle dynamic parameters in URL in Golang

You could use the reflect package to iterate over the fields and set them by name. Be aware that the reflect package is arduous to use and comes with some dangers of panics if not used properly.

Also be aware that url.Values.Get only returns the first value (see https://godoc.org/net/url#Values.Get for details)

EDIT: I added code to account for the pointers in the struct. They are handled differently.

https://play.golang.org/p/AO4lYx7xka

package main

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

type Media struct {
    ID                         uint
    Key                        string
    RecordKey                  string
    RecordID                   string
    SystemMediaKey             string
    MediaObjectID              string
    ChangedByID                string
    ChangedByKey               string
    MediaCategory              string
    MimeType                   string
    ShortDescription           string
    LongDescription            string
    EntryTimestamp             time.Time
    ModificationTimestamp      time.Time
    DeletedAtTimestamp         *time.Time
    MediaModificationTimestamp time.Time
    MediaURL                   string
    MediaHTML                  string
    Order                      int
    Group                      string
    Width                      int
    Height                     int
    ImageSize                  string
    ResourceName               string
    ClassName                  string
    Permission                 *string
    MediaStatus                string
}

func main() {

    testUrl := "www.example.com/test?MimeType=themimetype&Key=thekey&Permission=admin"

    u, err := url.Parse(testUrl)
    if err != nil {
        fmt.Println(err)
        return
    }

    params := u.Query()

    media := &Media{}

    val := reflect.ValueOf(media)

    for i := 0; i < val.Elem().NumField(); i++ {
        // get the reflect.StructField so we can get the Name
        f := val.Elem().Type().Field(i)

        // check if URL.Values contains the field
        if v := params.Get(f.Name); v != "" {
            // get the reflect.Value associated with the Field
            field := val.Elem().FieldByName(f.Name)

            kind := field.Kind()

            // you must switch for each reflect.Kind (associated with the type in your struct)
            // so you know which Set... method to call
            switch kind {
            case reflect.String:
                field.SetString(v)
            case reflect.Ptr:
                // pointers are a special case that must be handled manually unfortunately.
                // because they default to nil, calling Elem() won't reveal the underlying type
                // so you must simply string match the struct values that are pointers.
                switch f.Name {
                case "Permission":
                    newVal := reflect.New(reflect.TypeOf(v))
                    newVal.Elem().SetString(v)
                    field.Set(newVal.Elem().Addr())
                case "DeletedAtTimestamp":
                }
            }

        }
    }

    fmt.Printf("%#v\n", media)
    fmt.Println(*media.Permission)
}

I finally managed to use this library that converts a map to a struct. The only thing, is that I had to pre-process the map that is returned by URL.Query() Values because it returns an array for each value and I needed only the value and not inside an array.