getting variable amount in execute_payment_json - node.js

Question

I want to integrate Paypal in my site for which I am using Paypal-rest-sdk.
I want the amount in execute_payment_json to be equal to the amount that the user inputs.
paypal community has a thread on it but its not answered.
Check it here
The code that i run after getting the value from user
app.post("/paypal-pay",(req,res) => {
console.log(req.body.amount);
const create_payment_json = {
"intent": "sale",
"payer": {
"payment_method": "paypal"
},
"redirect_urls": {
"return_url": "http://localhost:3000/success",
"cancel_url": "http://localhost:3000/cancel"
},
"transactions": [{
"item_list": {
"items": [{
"name": "Donation",
"sku": "item",
"price": req.body.amount,
"currency": "USD",
"quantity": 1
}]
},
"amount": {
"currency": "USD",
"total": req.body.amount
},
"description": "The Donation that you are doing"
}]
};
paypal.payment.create(create_payment_json, function (error, payment) {
if (error) {
throw error;
} else {
console.log(payment);
payment.links.forEach(url => {
if(url.rel === "approval_url"){
res.redirect(url.href);
}
});
}
});
})
After success the above code redirects me to /success and in this i want the total to be equal to the value provided.
app.get("/success",(req,res)=>{
console.log(req.body);
const payerId = req.query.PayerID;
const paymentId = req.query.paymentId;
const execute_payment_json = {
"payer_id" : payerId,
"transactions": [{
"amount": {
"currency": "USD",
// I want this total to be equal to the payment provided by user.
"total": "1.00"
}
}]
}