added port config for heroku deployment

main.go

@@ -7,12 +7,14 @@ import (
 	"github.com/gorilla/mux"
 	"log"
 	"net/http"
+	"os"
 )
 
 func main() {
 
 
 	r := mux.NewRouter()
+	port := os.Getenv("PORT")
 	c := r.PathPrefix("/conservation/v1").Methods("GET").Subrouter()
 
 	// two handlerpaths makes sure that the caller does not HAVE to specify limit
@@ -30,7 +32,7 @@ func main() {
 		HandlerFunc(dHandler)
 
 	http.Handle("/", r)
-	log.Fatal(http.ListenAndServe(":5000", nil))
+	log.Fatal(http.ListenAndServe(":"+port, nil))
 
 }