While starting ember server I'm getting this error like SyntaxError: Unexpected identifier async postBuild()

While starting ember server I'm getting this error What could be the reason for this error?

Unexpected identifier
/Users/chraju/Desktop/sites/blog-front-end/node_modules/ember-cli-typescript/js/addon.js:47
    async postBuild() {
          ^^^^^^^^^

SyntaxError: Unexpected identifier
    at createScript (vm.js:56:10)
    at Object.runInThisContext (vm.js:97:10)
    at Module._compile (module.js:549:28)
    at Object.Module._extensions..js (module.js:586:10)
    at Module.load (module.js:494:32)
    at tryModuleLoad (module.js:453:12)
    at Function.Module._load (module.js:445:3)
    at Module.require (module.js:504:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/Users/chraju/Desktop/sites/blog-front-end/node_modules/ember-cli-typescript/index.js:9:20)