func NewLoaderCollection() LoaderCollection {
	return LoaderCollection{
		dataloaderFuncMap: map[key]dataloader.BatchFunc{
			userLoaderKey: newUserLoader(),
		},
	}
}
Initialize a lookup map of context keys to batch functions.

When Attach is called on the Collection, the batch functions are used to create new dataloader
instances. The instances are attached to the request context at the provided keys.

The keys are then used to extract the dataloader instances from the request context.
package loader
import (
	"fmt"
	"golang.org/x/net/context"
	"gopkg.in/nicksrandall/dataloader.v5"
)
type key string
const (
	userLoaderKey key = "user"
)