specify version

Program.cs

using Microsoft.OpenApi.Models;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
// バージョンの指定
builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v2", new OpenApiInfo { Title = "My API", Version = "v2" });
});
var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    // エンドポイントの指定
    app.UseSwaggerUI(config =>
    {
        config.SwaggerEndpoint("/swagger/v2/swagger.json", "API v2");
    });
}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();