1. 手动添加Lambda自定义函数：将下面的Lambda函数应用于AWS Amplify构建项目。

const AWS = require('aws-sdk');
const region = 'us-east-1';
const sns = new AWS.SNS({ region });
exports.handler = async (event, context) => {
  console.log(JSON.stringify(event, null, 2));
  const response = event.request;
  const userAttributes = response.userAttributes;
  const phoneNumber = userAttributes.phone_number;
  const message = `Hi ${userAttributes.name}, Thanks for signing up.`
  const params = {
    Message: message,
    PhoneNumber: phoneNumber
  };
  return new Promise((resolve, reject) => {
    sns.publish(params, (err, data) => {
      if (err) {
        console.error(err);
        reject(err);
      } else {
        console.log(data);
        resolve(event);
      }
    });
  });
};

2. 将以下代码添加到amplify/backend/function/postConfirmation/appsync-post-confirmation.yml文件中，以确保每次部署时都会再次部署Lambda函数。

Resources:
  AppSyncPostConfirmation:
    Type: 'AWS::Serverless::Function'
    Properties:
      CodeUri: ../amplify/backend/function/lambdaPostConfirmation/src
      Handler: app.handler
      Runtime: nodejs12.x
      MemorySize: 128
  LambdaRemove:
    Type: 'AWS::Serverless::Function'
    Properties:
      CodeUri: ../amplify/backend/function/lambdaPostRemove/src
      Handler: app.handler
      Runtime: nodejs12.x
      MemorySize: 128
  LambdaUpdate:
    Type: 'AWS::Serverless::Function'
    Properties:
      CodeUri: ../amplify/backend/function/lambdaPostUpdate/src
      Handler: app.handler
      Runtime: nodejs12.x
      MemorySize: 128
... // the rest of the AppSync template

这样，AWS Amplify将在每次部署更新时重新部署Lambda函数，以确保函数不会丢失。