Startup.cs

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.IdentityModel.Tokens;
using Microsoft.OpenApi.Models;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SwaggerJWT
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.  
        public void ConfigureServices(IServiceCollection services)
        {

            services.AddControllers();
            services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("ConnStr")));

            // For Identity  
            services.AddIdentity<ApplicationUser, IdentityRole>()
                .AddEntityFrameworkStores<ApplicationDbContext>()
                .AddDefaultTokenProviders();

            // Adding Authentication  
            services.AddAuthentication(options =>
            {
                options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
                options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
                options.DefaultScheme = JwtBearerDefaults.AuthenticationScheme;
            })

            // Adding Jwt Bearer  
            .AddJwtBearer(options =>
            {
                options.SaveToken = true;
                options.RequireHttpsMetadata = false;
                options.TokenValidationParameters = new TokenValidationParameters()
                {
                    ValidateIssuer = true,
                    ValidateAudience = true,
                    ValidAudience = Configuration["JWT:ValidAudience"],
                    ValidIssuer = Configuration["JWT:ValidIssuer"],
                    IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["JWT:Secret"]))
                };
            });

            services.AddSwaggerGen(swagger =>
            {
                //This is to generate the Default UI of Swagger Documentation    
                swagger.SwaggerDoc("v1", new OpenApiInfo
                {
                    Version = "v1",
                    Title = "ASP.NET 5 Web API",
                    Description = "Authentication and Authorization in ASP.NET 5 with JWT and Swagger"
                });
                // To Enable authorization using Swagger (JWT)    
                swagger.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme()
                {
                    Name = "Authorization",
                    Type = SecuritySchemeType.ApiKey,
                    Scheme = "Bearer",
                    BearerFormat = "JWT",
                    In = ParameterLocation.Header,
                    Description = "Enter 'Bearer' [space] and then your valid token in the text input below.\r\n\r\nExample: \"Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9\"",
                });
                swagger.AddSecurityRequirement(new OpenApiSecurityRequirement
                {
                    {
                          new OpenApiSecurityScheme
                            {
                                Reference = new OpenApiReference
                                {
                                    Type = ReferenceType.SecurityScheme,
                                    Id = "Bearer"
                                }
                            },
                            new string[] {}

                    }
                });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.  
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseSwagger();
            app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "ASP.NET 5 Web API v1"));

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}