move database connection into separate file

app.js

@@ -4,20 +4,20 @@ const jwt = require('jsonwebtoken')
 const { v1: uuidv1, NIL } = require('uuid');
 const reqPromise = require('request-promise')
 const mongoose = require('mongoose')
-const dotevn = require('dotenv')
-dotevn.config()
-const uri = `mongodb+srv://${process.env.DB_username}:${process.env.DB_password}@cluster0.f2gkp.mongodb.net/BelayChainNode1?retryWrites=true&w=majority`
+const Blockchain = require('./src/Blockchain');
+const connectDatabase = require('./database/database')
+
 const { Schema } = mongoose
-// const port = process.env.PORT || 9000
 const port = process.argv[2]
 const corsOptions = {
     origin: '*',
     methods: 'GET,POST,PUT,PATCH,DELETE'
 }
-const Blockchain = require('./src/Blockchain');
-const bodyParser = require('body-parser');
 const app = express();
 
+app.use(cors(corsOptions))
+app.use(express.json())
+
 const blockSchema = new Schema({
     index: Number,
     timestamp: Number,
@@ -35,14 +35,6 @@ const Block = mongoose.model('Block', blockSchema)
 const Node = mongoose.model('Node', nodeSchema)
 
 
-app.use(cors(corsOptions))
-app.use(express.json())
-
-mongoose.connect(uri, {useNewUrlParser: true, useUnifiedTopology: true})
-    .then(() => console.log("MONGODB CONNECTED"))
-    .catch(console.error)
-
-
 let BelayChain = []
 
 const loadBelayChain = () => {

database/database.js

@@ -0,0 +1,8 @@
+const dotevn = require('dotenv')
+dotevn.config()
+const uri = `mongodb+srv://${process.env.DB_username}:${process.env.DB_password}@cluster0.f2gkp.mongodb.net/BelayChainNode1?retryWrites=true&w=majority`
+const mongoose = require('mongoose')
+
+module.exports = mongoose.connect(uri, {useNewUrlParser: true, useUnifiedTopology: true})
+                    .then(() => console.log("MONGODB CONNECTED"))
+                    .catch(console.error)