func NewGateway(h http.Handler) *Gateway {
	return &Gateway{h: h}
}
NewGateway creates a gateway using the provided http.Handler enabling use in existing aws-lambda-go
projects
package gateway
import (
	"context"
	"encoding/json"
	"net/http"
	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
)
func ListenAndServe(addr string, h http.Handler) error {
	if h == nil {
		h = http.DefaultServeMux
	}
	gw := NewGateway(h)
	lambda.StartHandler(gw)
	return nil
}