角度错误：http：// localhost：3000 / login的Http失败响应：404 not found

Question

I want to get login information that user enters at backend. Here is the backend code :-

package main

import (

    "fmt"
    "net/http"
    "github.com/gorilla/mux"
    "github.com/gorilla/handlers"
    "encoding/json"
    "log"
)

type LoginDetails struct {
   Username string `json:"username"` 
   Password string `json:"password"`
}

func login(w http.ResponseWriter, req *http.Request) {
    var loginData LoginDetails
    err := json.NewDecoder(req.Body).Decode(&loginData)
    if err!=nil{
        panic(err)
    }
}

func main() {
    fmt.Println("Starting server at http://localhost:3000...")
    router := mux.NewRouter()
    router.PathPrefix("/").Handler(http.FileServer(http.Dir("./static/dist/static")))
    router.HandleFunc("/login", login)

    headersOk := handlers.AllowedHeaders([]string{"Authorization"})
    methodsOk := handlers.AllowedMethods([]string{"GET", "POST", "OPTIONS"})
    log.Fatal(http.ListenAndServe(":3000", handlers.CORS( headersOk, methodsOk)(router)))
}

Angular code :-

login.component.ts file :-

import { Component, OnInit } from '@angular/core';
import { FormGroup, FormControl, FormBuilder } from '@angular/forms';
import { HttpErrorResponse} from '@angular/common/http';
import { LoginService } from './login.service';
import { LoginDetails } from './login';

@Component({
  selector: 'app-login',
  templateUrl: './login.component.html',
  styleUrls: ['./login.component.css'],
  providers : [LoginService, LoginDetails]
})
export class LoginComponent implements OnInit {

  loginForm : FormGroup; 
  constructor(private loginData : LoginDetails,  private loginservice:  LoginService, private _formBuilder : FormBuilder){}

  ngOnInit() {
    this.loginForm = this._formBuilder.group({
      username : ['username'], 
      password : ['password']
    })
  }

  OnSubmit(){
      this.loginData.username = this.loginForm.controls.username.value;
      this.loginData.password = this.loginForm.controls.password.value;

      this.loginservice.loginUser(this.loginData).subscribe(response => {
          console.log(response)
      },(err: HttpErrorResponse) => {
          console.log(err);
      });
  }

}

login.service.ts file :-

import { Injectable } from '@angular/core';
import { HttpClient, HttpClientModule, HttpHeaders} from '@angular/common /http';
import { Observable } from 'rxjs';
import { LoginDetails } from './login'


@Injectable()

export class LoginService{

    private _url : string = "http://localhost:3000/login";
    constructor( private http : HttpClient){}

    loginUser(loginData : LoginDetails): Observable <any>{
        console.log(loginData)
        return this.http.post(this._url, loginData, {responseType : 'text'});   
    }
}

Error I receive is this :- POST http://localhost:3000/login 404 (Not Found).