I am follow this steps to add basic auth to treafik 2.1.6,first create kuberntes(v1.15.2) secret:

openssl rand -base64 32
htpasswd -bc auth dabai-admin hbzwvEbfRGSN4MAiycCVM30stfGjzR6dZPDh9bS5te4=
kubectl create secret generic treafik-secret-name --from-file=auth -n kube-system

create middleware:

apiVersion: traefik.containo.us/v1alpha1
kind: Middleware
metadata:
  name: basic-auth
spec:
  basicAuth:
    secret: treafik-secret-name

tweak traefik config and add middleware we create:

apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
  name: traefik-dashboard-route
annotations:
  kubernetes.io/ingress.class: traefik
  ingress.kubernetes.io/auth-type: basic
  ingress.kubernetes.io/auth-secret: traefik-secret-name
spec:
  entryPoints:
    - web
  routes:
    - match: Host(`traefik.example.com`) && (PathPrefix(`/dashboard`) || PathPrefix(`/api`))
      kind: Rule
      services:
        - name: traefik
          port: 8080
      middlewares:
        - name: basic-auth

finally when I access the domain traefik.example.com,it give me this tips:404 page not found.something is misssing with traefik basic auth? what should I do to make it right?The expect action is show the login popup form, enter password correct could login success.