Node Async not executing the db function - node.js

Question

I am sending a post request from a form but async.waterfall() doesn't execute the mongoose's User.find() function to fetch users from the database and as a result the post request's status in the network inspector is pending as res.send() is not being called.
exports.createUser = function(req,res){
var email1 = req.body.mail.toString();
var password = req.body.password.toString();
async.waterfall([
function(callback) {
// verify user in the db
User.find({email:email1},function(err,data){
if (err){
res.send(404);
return callback(err);
}
// user is found
if (data.length != 0){
res.send(404);
return callback(new Error("User Found"));
}
callback();
});
},
// generate salt password
function(callback) {
bcrypt.genSalt(SALT_WORK_FACTOR,function(err,salt){
if (err) return callback(err);
bcrypt.hash(password,salt,function(err,hash){
if (err) return callback(err);
return callback(null,hash);
});
});
},
//generate random string
function(hash,callback){
crypto.randomBytes(48,function(err,buf){
if (err) return callback(err);
var randomString = buf.toString('hex');
return callback(null,hash,randomString);
});
},
// save them in the mongoDb using mongoose
function(hash,randomString,callback){
var userModel = new User;
userModel.email = email1;
userModel.password = hash;
userModel.verificationId = randomString;
userModel.save();
callback(null,'done');
}
],function(err){
if (err){
console.log(err);
res.send(404);
} else{
console.log("done");
res.send("200");
}
});
}
Here is my app.js file using express
// render the registration page
app.get('/users/create',register.renderUserPage);
app.post('/users/create',function(req,res){
register.createUser(req,res);
});
Here is the Db.js file which connects to mongoDb using mongoose
console.log("connection succeeded");
var UserSchema = new Schema ({
email: {type:String ,require : true ,index : {unique : true}} ,
password:{ type : String ,required: true} ,
verificationId:{type:String, required:true,index:true}
});
UserSchema.plugin(ttl,{ttl:90000000});
module.exports = mongoose.model('User',UserSchema);