test = ()=> {
  return new Promise((resolve,reject)=>{
    try{
      setTimeout(()=> {resolve('Hello')},10000);

    }catch(e){
      reject('error')
    }

  })
}
requestCases = async () =>{

  let hello = await this.test();
  return hello;
}


...
this.requestCases().then((value)=>console.log(value));