无法在angular 9中将值从父组件传递到子组件

import { Component, Input } from '@angular/core';

@Component({
  selector: 'app-parent',
  template: `
    <app-child [childValue]="parentValue"></app-child>
  `
})
export class ParentComponent {
  parentValue: string = 'Hello from parent!';
}

import { Component, Input } from '@angular/core';

@Component({
  selector: 'app-child',
  template: `
    <p>{{ childValue }}</p>
  `
})
export class ChildComponent {
  @Input() childValue: string;
}