A push notification micro server using Gin framework written in Go (Golang) and see the demo app.
- gorush
- Support Firebase Cloud Messaging using go-fcm library for Android.
- Support HTTP/2 Apple Push Notification Service using apns2 library.
- Support YAML configuration.
- Support command line to send single Android or iOS notification.
- Support Web API to send push notification.
- Support HTTP/2 or HTTP/1.1 protocol.
- Support notification queue and multiple workers.
- Support
/api/stat/app
show notification success and failure counts. - Support
/api/config
show your YAML config. - Support store app stat to memory, Redis, BoltDB, BuntDB, LevelDB or BadgerDB.
- Support
p8
,p12
orpem
format of iOS certificate file. - Support
/sys/stats
show response time, status code count, etc. - Support for HTTP, HTTPS or SOCKS5 proxy.
- Support retry send notification if server response is fail.
- Support expose prometheus metrics.
- Support install TLS certificates from Let's Encrypt automatically.
- Support send notification through RPC protocol, we use gRPC as default framework.
- Support running in Docker, Kubernetes or AWS Lambda (Native Support in Golang)
- Support graceful shutdown that workers and queue have been sent to APNs/FCM before shutdown service.
See the default YAML config example:
core:
enabled: true # enable httpd server
address: "" # ip address to bind (default: any)
shutdown_timeout: 30 # default is 30 second
port: "8088" # ignore this port number if auto_tls is enabled (listen 443).
worker_num: 0 # default worker number is runtime.NumCPU()
queue_num: 0 # default queue number is 8192
max_notification: 100
sync: false # set true if you need get error message from fail push notification in API response.
feedback_hook_url: "" # set a hook url if you need get error message asynchronously from fail push notification in API response.
feedback_timeout: 10 # default is 10 second
mode: "release"
ssl: false
cert_path: "cert.pem"
key_path: "key.pem"
cert_base64: ""
key_base64: ""
http_proxy: ""
pid:
enabled: false
path: "gorush.pid"
override: true
auto_tls:
enabled: false # Automatically install TLS certificates from Let's Encrypt.
folder: ".cache" # folder for storing TLS certificates
host: "" # which domains the Let's Encrypt will attempt
grpc:
enabled: false # enable gRPC server
port: 9000
api:
push_uri: "/api/push"
stat_go_uri: "/api/stat/go"
stat_app_uri: "/api/stat/app"
config_uri: "/api/config"
sys_stat_uri: "/sys/stats"
metric_uri: "/metrics"
health_uri: "/healthz"
android:
enabled: true
apikey: "YOUR_API_KEY"
max_retry: 0 # resend fail notification, default value zero is disabled
ios:
enabled: false
key_path: "key.pem"
key_base64: "" # load iOS key from base64 input
key_type: "pem" # could be pem, p12 or p8 type
password: "" # certificate password, default as empty string.
production: false
max_concurrent_pushes: 100 # just for push ios notification
max_retry: 0 # resend fail notification, default value zero is disabled
key_id: "" # KeyID from developer account (Certificates, Identifiers & Profiles -> Keys)
team_id: "" # TeamID from developer account (View Account -> Membership)
log:
format: "string" # string or json
access_log: "stdout" # stdout: output to console, or define log path like "log/access_log"
access_level: "debug"
error_log: "stderr" # stderr: output to console, or define log path like "log/error_log"
error_level: "error"
hide_token: true
stat:
engine: "memory" # support memory, redis, boltdb, buntdb or leveldb
redis:
addr: "localhost:6379"
password: ""
db: 0
boltdb:
path: "bolt.db"
bucket: "gorush"
buntdb:
path: "bunt.db"
leveldb:
path: "level.db"
badgerdb:
path: "badger.db"
Memory average usage: 28Mb (the total bytes of memory obtained from the OS.)
Test Command (We use bat as default cli tool.):
for i in {1..9999999}; do bat -b.N=1000 -b.C=100 POST localhost:8088/api/push notifications:[email protected]; sleep 1; done
How to send push notification using gorush
command? (Android or iOS)
The pre-compiled binaries can be downloaded from release page.
With Go
installed
go get -u -v github.com/appleboy/gorush
On linux
wget https://github.com/appleboy/gorush/releases/download/v1.13.0/gorush-v1.13.0-linux-amd64 -O gorush
On OS X
wget https://github.com/appleboy/gorush/releases/download/v1.13.0/gorush-v1.13.0-darwin-amd64 -O gorush
On Windows
wget https://github.com/appleboy/gorush/releases/download/v1.13.0/gorush-v1.13.0-windows-amd64.exe -O gorush.exe
On macOS, use Homebrew.
brew install --HEAD https://github.com/appleboy/gorush/raw/master/HomebrewFormula/gorush.rb
Gorush uses the Go Modules support built into Go 1.11 to build. The easiest way to get started is to clone Gorush in a directory outside of the GOPATH, as in the following example:
mkdir $HOME/src
cd $HOME/src
git clone https://github.com/appleboy/gorush.git
cd gorush
go install
________ .__
/ _____/ ____ _______ __ __ ______| |__
/ \ ___ / _ \\_ __ \| | \/ ___/| | \
\ \_\ \( <_> )| | \/| | /\___ \ | Y \
\______ / \____/ |__| |____//____ >|___| /
\/ \/ \/
Usage: gorush [options]
Server Options:
-A, --address <address> Address to bind (default: any)
-p, --port <port> Use port for clients (default: 8088)
-c, --config <file> Configuration file path
-m, --message <message> Notification message
-t, --token <token> Notification token
-e, --engine <engine> Storage engine (memory, redis ...)
--title <title> Notification title
--proxy <proxy> Proxy URL (support http, https, or socks5)
--pid <pid path> Process identifier path
--redis-addr <redis addr> Redis addr (default: localhost:6379)
iOS Options:
-i, --key <file> certificate key file path
-P, --password <password> certificate key password
--ios enabled iOS (default: false)
--production iOS production mode (default: false)
Android Options:
-k, --apikey <api_key> Android API Key
--android enabled android (default: false)
Common Options:
--topic <topic> iOS or Android topic message
-h, --help Show this message
-v, --version Show version
Send single notification with the following command.
gorush -android -m "your message" -k "API Key" -t "Device token"
Send messages to topics.
gorush --android --topic "/topics/foo-bar" \
-m "This is a Firebase Cloud Messaging Topic Message" \
-k your_api_key
-m
: Notification message.-k
: Firebase Cloud Messaging api key-t
: Device token.--title
: Notification title.--topic
: Send messages to topics. note: don't add device token.--proxy
: Sethttp
,https
orsocks5
proxy url.
Send single notification with the following command.
$ gorush -ios -m "your message" -i "your certificate path" \
-t "device token" --topic "apns topic"
-m
: Notification message.-i
: Apple Push Notification Certificate path (pem
orp12
file).-t
: Device token.--title
: Notification title.--topic
: The topic of the remote notification.--password
: The certificate password.
The default endpoint is APNs development. Please add -production
flag for APNs production push endpoint.
$ gorush -ios -m "your message" -i "your certificate path" \
-t "device token" \
-production
Send single notification with the following command:
gorush -android -m "your message" -k "API key" -t "Device token"
Please make sure your config.yml exist. Default port is 8088
.
# for default config
$ gorush
# for custom config file
$ gorush -c config.yml
Get go status of api server using httpie tool:
http -v --verify=no --json GET http://localhost:8088/api/stat/go
Gorush support the following API.
- GET
/api/stat/go
Golang cpu, memory, gc, etc information. Thanks for golang-stats-api-handler. - GET
/api/stat/app
show notification success and failure counts. - GET
/api/config
show server yml config file. - POST
/api/push
push ios and android notifications.
Golang cpu, memory, gc, etc information. Response with 200
http status code.
{
"time": 1460686815848046600,
"go_version": "go1.6.1",
"go_os": "darwin",
"go_arch": "amd64",
"cpu_num": 4,
"goroutine_num": 15,
"gomaxprocs": 4,
"cgo_call_num": 1,
"memory_alloc": 7455192,
"memory_total_alloc": 8935464,
"memory_sys": 12560632,
"memory_lookups": 17,
"memory_mallocs": 31426,
"memory_frees": 11772,
"memory_stack": 524288,
"heap_alloc": 7455192,
"heap_sys": 8912896,
"heap_idle": 909312,
"heap_inuse": 8003584,
"heap_released": 0,
"heap_objects": 19654,
"gc_next": 9754725,
"gc_last": 1460686815762559700,
"gc_num": 2,
"gc_per_second": 0,
"gc_pause_per_second": 0,
"gc_pause": [
0.326576,
0.227096
]
}
Show success or failure counts information of notification.
{
"version": "v1.6.2",
"queue_max": 8192,
"queue_usage": 0,
"total_count": 77,
"ios": {
"push_success": 19,
"push_error": 38
},
"android": {
"push_success": 10,
"push_error": 10
}
}
Show response time, status code count, etc.
{
"pid": 80332,
"uptime": "1m42.428010614s",
"uptime_sec": 102.428010614,
"time": "2016-06-26 12:27:11.675973571 +0800 CST",
"unixtime": 1466915231,
"status_code_count": { },
"total_status_code_count": {
"200": 5
},
"count": 0,
"total_count": 5,
"total_response_time": "10.422441ms",
"total_response_time_sec": 0.010422441000000001,
"average_response_time": "2.084488ms",
"average_response_time_sec": 0.0020844880000000002
}
Support expose prometheus metrics.
Simple send iOS notification example, the platform
value is 1
:
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"message": "Hello World iOS!"
}
]
}
Simple send Android notification example, the platform
value is 2
:
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World Android!"
}
]
}
Simple send notification on Android and iOS devices using Firebase, the platform
value is 2
:
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "This notification will go to iOS and Android platform via Firebase!"
}
]
}
Send multiple notifications as below:
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"message": "Hello World iOS!"
},
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World Android!"
},
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World!"
},
.....
]
}
See more example about iOS or Android.
The Request body must have a notifications array. The following is a parameter table for each notification.
name | type | description | required | note |
---|---|---|---|---|
notif_id | string | A unique string that identifies the notification for async feedback | - | |
tokens | string array | device tokens | o | |
platform | int | platform(iOS,Android) | o | 1=iOS, 2=Android (Firebase) |
message | string | message for notification | - | |
title | string | notification title | - | |
priority | string | Sets the priority of the message. | - | normal or high |
content_available | bool | data messages wake the app by default. | - | |
sound | interface{} | sound type | - | |
data | string array | extensible partition | - | |
retry | int | retry send notification if fail response from server. Value must be small than max_retry field. |
- | |
topic | string | send messages to topics | ||
image | string | image url to show in notification | - | only Android |
api_key | string | api key for firebase cloud message | - | only Android |
to | string | The value must be a registration token, notification key, or topic. | - | only Android |
collapse_key | string | a key for collapsing notifications | - | only Android |
delay_while_idle | bool | a flag for device idling | - | only Android |
time_to_live | uint | expiration of message kept on FCM storage | - | only Android |
restricted_package_name | string | the package name of the application | - | only Android |
dry_run | bool | allows developers to test a request without actually sending a message | - | only Android |
notification | string array | payload of a FCM message | - | only Android. See the detail |
expiration | int | expiration for notification | - | only iOS |
apns_id | string | A canonical UUID that identifies the notification | - | only iOS |
collapse_id | string | An identifier you use to coalesce multiple notifications into a single notification for the user | - | only iOS |
push_type | string | The type of the notification. The value of this header is alert or background. | - | only iOS |
badge | int | badge count | - | only iOS |
category | string | the UIMutableUserNotificationCategory object | - | only iOS |
alert | string array | payload of a iOS message | - | only iOS. See the detail |
mutable_content | bool | enable Notification Service app extension. | - | only iOS(10.0+). |
name | string | sets the name value on the aps sound dictionary. | - | only iOS |
volume | float32 | sets the volume value on the aps sound dictionary. | - | only iOS |
name | type | description | required | note |
---|---|---|---|---|
title | string | Apple Watch & Safari display this string as part of the notification interface. | - | |
body | string | The text of the alert message. | - | |
subtitle | string | Apple Watch & Safari display this string as part of the notification interface. | - | |
action | string | The label of the action button. This one is required for Safari Push Notifications. | - | |
action-loc-key | string | If a string is specified, the system displays an alert that includes the Close and View buttons. | - | |
launch-image | string | The filename of an image file in the app bundle, with or without the filename extension. | - | |
loc-args | array of strings | Variable string values to appear in place of the format specifiers in loc-key. | - | |
loc-key | string | A key to an alert-message string in a Localizable.strings file for the current localization. | - | |
title-loc-args | array of strings | Variable string values to appear in place of the format specifiers in title-loc-key. | - | |
title-loc-key | string | The key to a title string in the Localizable.strings file for the current localization. | - |
See more detail about APNs Remote Notification Payload.
name | type | description | required | note |
---|---|---|---|---|
name | string | sets the name value on the aps sound dictionary. | - | |
volume | float32 | sets the volume value on the aps sound dictionary. | - | |
critical | int | sets the critical value on the aps sound dictionary. | - |
request format:
{
"sound": {
"critical": 1,
"name": "default",
"volume": 2.0
}
}
name | type | description | required | note |
---|---|---|---|---|
icon | string | Indicates notification icon. | - | |
tag | string | Indicates whether each notification message results in a new entry on the notification center on Android. | - | |
color | string | Indicates color of the icon, expressed in #rrggbb format | - | |
click_action | string | The action associated with a user click on the notification. | - | |
body_loc_key | string | Indicates the key to the body string for localization. | - | |
body_loc_args | string | Indicates the string value to replace format specifiers in body string for localization. | - | |
title_loc_key | string | Indicates the key to the title string for localization. | - | |
title_loc_args | string | Indicates the string value to replace format specifiers in title string for localization. | - |
See more detail about Firebase Cloud Messaging HTTP Protocol reference.
Send normal notification.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"message": "Hello World iOS!"
}
]
}
The following payload asks the system to display an alert with a Close button and a single action button.The title and body keys provide the contents of the alert. The “PLAY” string is used to retrieve a localized string from the appropriate Localizable.strings file of the app. The resulting string is used by the alert as the title of an action button. This payload also asks the system to badge the app’s icon with the number 5.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"badge": 5,
"alert": {
"title" : "Game Request",
"body" : "Bob wants to play poker",
"action-loc-key" : "PLAY"
}
}
]
}
The following payload specifies that the device should display an alert message, plays a sound, and badges the app’s icon.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"message": "You got your emails.",
"badge": 9,
"sound": {
"critical": 1,
"name": "default",
"volume": 1.0
}
}
]
}
Add other fields which user defined via data
field.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
"message": "Hello World iOS!",
"data": {
"key1": "welcome",
"key2": 2
}
}
]
}
Support send notification from different environment. See the detail of issue.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 1,
+ "production": true,
"message": "Hello World iOS Production!"
},
{
"tokens": ["token_a", "token_b"],
"platform": 1,
+ "development": true,
"message": "Hello World iOS Sandbox!"
}
]
}
Send normal notification.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World Android!",
"title": "You got message"
}
]
}
Add notification
payload.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World Android!",
"title": "You got message",
"notification" : {
"icon": "myicon",
"color": "#112244"
}
}
]
}
Add other fields which user defined via data
field.
{
"notifications": [
{
"tokens": ["token_a", "token_b"],
"platform": 2,
"message": "Hello World Android!",
"title": "You got message",
"data": {
"Nick" : "Mario",
"body" : "great match!",
"Room" : "PortugalVSDenmark"
}
}
]
}
Send messages to topics
{
"notifications": [
{
"to": "/topics/foo-bar",
"platform": 2,
"message": "This is a Firebase Cloud Messaging Topic Message"
}
]
}
Error response message table:
status code | message |
---|---|
400 | Missing notifications field. |
400 | Notifications field is empty. |
400 | Number of notifications(50) over limit(10) |
Success response:
{
"counts": 60,
"logs": [],
"success": "ok"
}
If you need error logs from sending fail notifications, please set a feedback_hook_url
. The server with send the failing logs asynchronously to your API as POST
requests.
core:
port: "8088" # ignore this port number if auto_tls is enabled (listen 443).
worker_num: 0 # default worker number is runtime.NumCPU()
queue_num: 0 # default queue number is 8192
max_notification: 100
sync: false
- feedback_hook_url: ""
+ feedback_hook_url: "https://exemple.com/api/hook"
You can also switch to sync mode by setting the sync
value as true
on yaml config.
core:
port: "8088" # ignore this port number if auto_tls is enabled (listen 443).
worker_num: 0 # default worker number is runtime.NumCPU()
queue_num: 0 # default queue number is 8192
max_notification: 100
- sync: false
+ sync: true
See the following error format.
{
"counts": 60,
"logs": [
{
"type": "failed-push",
"platform": "android",
"token": "*******",
"message": "Hello World Android!",
"error": "InvalidRegistration"
},
{
"type": "failed-push",
"platform": "ios",
"token": "*****",
"message": "Hello World iOS1111!",
"error": "Post https://api.push.apple.com/3/device/bbbbb: remote error: tls: revoked certificate"
},
{
"type": "failed-push",
"platform": "ios",
"token": "*******",
"message": "Hello World iOS222!",
"error": "Post https://api.push.apple.com/3/device/token_b: remote error: tls: revoked certificate"
}
],
"success": "ok"
}
Gorush support gRPC service. You can enable the gRPC in config.yml
, default as disabled. Enable the gRPC server:
GORUSH_GRPC_ENABLED=true GORUSH_GRPC_PORT=3000 gorush
The following example code to send single notification in Go.
package main
import (
"context"
"log"
"github.com/appleboy/gorush/rpc/proto"
structpb "github.com/golang/protobuf/ptypes/struct"
"google.golang.org/grpc"
)
const (
address = "localhost:9000"
)
func main() {
// Set up a connection to the server.
conn, err := grpc.Dial(address, grpc.WithInsecure())
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
c := proto.NewGorushClient(conn)
r, err := c.Send(context.Background(), &proto.NotificationRequest{
Platform: 2,
Tokens: []string{"1234567890"},
Message: "test message",
Badge: 1,
Category: "test",
Sound: "test",
Alert: &proto.Alert{
Title: "Test Title",
Body: "Test Alert Body",
Subtitle: "Test Alert Sub Title",
LocKey: "Test loc key",
LocArgs: []string{"test", "test"},
},
Data: &structpb.Struct{
Fields: map[string]*structpb.Value{
"key1": {
Kind: &structpb.Value_StringValue{StringValue: "welcome"},
},
"key2": {
Kind: &structpb.Value_NumberValue{NumberValue: 2},
},
},
},
})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Success: %t\n", r.Success)
log.Printf("Count: %d\n", r.Counts)
}
See the Node.js example and see more detail frome README:
var messages = require('./gorush_pb');
var services = require('./gorush_grpc_pb');
var grpc = require('grpc');
function main() {
var client = new services.GorushClient('localhost:9000',
grpc.credentials.createInsecure());
var request = new messages.NotificationRequest();
var alert = new messages.Alert();
request.setPlatform(2);
request.setTokensList(["1234567890"]);
request.setMessage("Hello!!");
request.setTitle("hello2");
request.setBadge(2);
request.setCategory("mycategory");
request.setSound("sound")
alert.setTitle("title");
request.setAlert(alert);
request.setThreadid("threadID");
request.setContentavailable(false);
request.setMutablecontent(false);
client.send(request, function (err, response) {
if(err) {
console.log(err);
} else {
console.log("Success:", response.getSuccess());
console.log("Counts:", response.getCounts());
}
});
}
main();
GRPC Health Checking example: See document.
package main
import (
"context"
"log"
"github.com/appleboy/gorush/rpc/proto"
structpb "github.com/golang/protobuf/ptypes/struct"
"google.golang.org/grpc"
)
const (
address = "localhost:9000"
)
func main() {
// Set up a connection to the server.
conn, err := grpc.Dial(address, grpc.WithInsecure())
if err != nil {
log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
c := proto.NewGorushClient(conn)
r, err := c.Send(context.Background(), &proto.NotificationRequest{
Platform: 2,
Tokens: []string{"1234567890"},
Message: "test message",
Badge: 1,
Category: "test",
Sound: "test",
Alert: &proto.Alert{
Title: "Test Title",
Body: "Test Alert Body",
Subtitle: "Test Alert Sub Title",
LocKey: "Test loc key",
LocArgs: []string{"test", "test"},
},
Data: &structpb.Struct{
Fields: map[string]*structpb.Value{
"key1": {
Kind: &structpb.Value_StringValue{StringValue: "welcome"},
},
"key2": {
Kind: &structpb.Value_NumberValue{NumberValue: 2},
},
},
},
})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Success: %t\n", r.Success)
log.Printf("Count: %d\n", r.Counts)
}
Set up gorush
in the cloud in under 5 minutes with zero knowledge of Golang or Linux shell using our gorush Docker image.
docker pull appleboy/gorush
docker run --name gorush -p 80:8088 appleboy/gorush
Run gorush
with your own config file.
docker pull appleboy/gorush
docker run --name gorush -v ${PWD}/config.yml:/config.yml -p 80:8088 appleboy/gorush
Testing your gorush server using httpie command.
http -v --verify=no --json GET http://your.docker.host/api/stat/go
Create namespace as gorush
as gorush
and then your configuration map:
kubectl create -f k8s/gorush-namespace.yaml
kubectl create -f k8s/gorush-configmap.yaml
Create redis service:
kubectl create -f k8s/gorush-redis-deployment.yaml
kubectl create -f k8s/gorush-redis-service.yaml
Create gorush deployment controller provides declarative updates for Pods and ReplicaSets:
kubectl create -f k8s/gorush-deployment.yaml
kubectl create -f k8s/gorush-service.yaml
Update the following in k8s/gorush-service.yaml
- type: LoadBalancer
- # type: NodePort
+ # type: LoadBalancer
+ type: NodePort
Then start the AWS ALB by the follwong command.
kubectl create -f k8s/gorush-service.yaml
kubectl create -f k8s/gorush-aws-alb-ingress.yaml
kubectl delete -f k8s
AWS excited to announce Go as a supported language for AWS Lambda. You’re going to create an application that uses an API Gateway event source to create a simple Hello World RESTful API.
Download source code first.
git clone https://github.com/appleboy/gorush.git
cd gorush && make build_linux_lambda
you can see the binary file in release/linux/lambda/
folder
we need to build a binary that will run on Linux, and ZIP it up into a deployment package.
zip deployment.zip release/linux/lambda/gorush
Upload the deployment.zip
via web UI or you can try the drone-lambda as the following command. it will zip your binary file and upload to AWS Lambda automatically.
$ AWS_ACCESS_KEY_ID=YOUR_AWS_ACCESS_KEY_ID \
AWS_SECRET_ACCESS_KEY=YOUR_AWS_SECRET_ACCESS_KEY \
drone-lambda --region ap-southeast-1 \
--function-name gorush \
--source release/linux/lambda/gorush
Or you can deploy gorush to alternative solution like netlify functions. Netlify lets you deploy serverless Lambda functions without an AWS account, and with function management handled directly within Netlify. Please see the netlify.toml file:
[build]
command = "./build.sh"
functions = "release/linux/lambda"
[build.environment]
GO_IMPORT_PATH = "github.com/appleboy/gorush"
GO111MODULE = "on"
[[redirects]]
from = "/*"
to = "/.netlify/functions/gorush/:splat"
status = 200
Copyright 2019 Bo-Yi Wu @appleboy.
Licensed under the MIT License.