I tried crud operation using nodejs and mongodb. all crud operation is working fine.but get method showing only one data not showing all data

I tried crud Operation using node js and mongodb.all crud operation working fine.but i tried to run get method its showing on;y one record.after i see my code its throwing error (Can't set headers after they are sent).How to solve this issue any one give suggestion.

index.js

router.get('/', async (req, res,next) => {
    (async function() {
        try {
          await client.connect();
          console.log("Connected correctly to server");
          const db = client.db('olc_prod_db');
          let r = await db.collection('Ecommerce').find();
          r.forEach(function(result,err)
          {
            res.send(result)
          })
          // Close connection
          client.close();
        } catch(err) {
          console.log(err.stack);
        }
      })();

  });

router.get('/', async (req, res,next) => {
(async function() {
    try {
      await client.connect();
      console.log("Connected correctly to server");
      const db = db.collection('Ecommerce').find({}).toArray(function(error, documents) {
        if (err) throw error;
        res.send(documents);
      });
    } catch(err) {
      console.log(err.stack);
    }
  })();

});

For each subsequent request, you have to 'send' once only. This method just completes the request cycle so you can't call it on loop because of loop run 'n' time.