How to override appsettings.json with environment variables?

How to override appsettings.json with environment variables for connection string in onconfiguring method in dbcontext class in ASP.NET Core 3.0 project ?

I wrote below code in

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

{

if (!optionsBuilder.IsConfigured)

{

IConfigurationRoot configuration = new ConfigurationBuilder()

.SetBasePath(AppDomain.CurrentDomain.BaseDirectory)

.AddJsonFile("appsettings.json")

.Build();

optionsBuilder.UseSqlServer(configuration.GetConnectionString("UserDBContext"));

}