Erro ao utilizar o pipe async

Boa noite Professor, Por favor, poderia me ajudar no erro apresentado(Não encontrei na vídeo aula o momento em que foi implementado o *ngIf do header.component.html):

compiler.js:215 Uncaught Error: Template parse errors:
The pipe 'async' could not be found ("
        <a class="navbar-brand">ALURAPIC</a>

        <div *[ERROR ->]ngIf="(user$ | async) as user; else login">
            <i class="fa fa-user-circle"></i>
         "): ng:///CoreModule/HeaderComponent.html@4:14
Can't bind to 'ngIf' since it isn't a known property of 'div'. ("
        <a class="navbar-brand">ALURAPIC</a>

        <div [ERROR ->]*ngIf="(user$ | async) as user; else login">
            <i class="fa fa-user-circle"></i>
        "): ng:///CoreModule/HeaderComponent.html@4:13
Can't bind to 'ngIfElse' since it isn't a known property of 'div'. ("
        <a class="navbar-brand">ALURAPIC</a>

        <div [ERROR ->]*ngIf="(user$ | async) as user; else login">
            <i class="fa fa-user-circle"></i>
        "): ng:///CoreModule/HeaderComponent.html@4:13
Property binding ngIf not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the "@NgModule.declarations". ("
        <a class="navbar-brand">ALURAPIC</a>

        [ERROR ->]<div *ngIf="(user$ | async) as user; else login">
            <i class="fa fa-user-circle"></i>
   "): ng:///CoreModule/HeaderComponent.html@4:8
Property binding ngIfElse not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the "@NgModule.declarations". ("
        <a class="navbar-brand">ALURAPIC</a>

        [ERROR ->]<div *ngIf="(user$ | async) as user; else login">
            <i class="fa fa-user-circle"></i>
   "): ng:///CoreModule/HeaderComponent.html@4:8
    at syntaxError (compiler.js:215)
    at TemplateParser.push../node_modules/@angular/compiler/fesm5/compiler.js.TemplateParser.parse (compiler.js:14702)
    at JitCompiler.push../node_modules/@angular/compiler/fesm5/compiler.js.JitCompiler._parseTemplate (compiler.js:22709)
    at JitCompiler.push../node_modules/@angular/compiler/fesm5/compiler.js.JitCompiler._compileTemplate (compiler.js:22696)
    at compiler.js:22639
    at Set.forEach (<anonymous>)
    at JitCompiler.push../node_modules/@angular/compiler/fesm5/compiler.js.JitCompiler._compileComponents (compiler.js:22639)
    at compiler.js:22549
    at Object.then (compiler.js:206)
    at JitCompiler.push../node_modules/@angular/compiler/fesm5/compiler.js.JitCompiler._compileModuleAndComponents (compiler.js:22548)