How to read the custom Provider parameters


I am looking for some help in order to read the parameters defined in the custom provider block

For ex:

    func Provider() terraform.ResourceProvider {
            return &schema.Provider{
                    Schema: map[string]*schema.Schema{
                            "myvar": &schema.Schema{
                                    Type:     schema.TypeString,
                                    Required: true,
                                    Description: "SCM Account var",

I do I read the “myvar” in resource_cert.go in the Terraform Create function?
If its a resource variable, I am able to read it using

myvar := d.Get(“myvar”).(string)
But how do I read the provider values declared in the or the *.auto.tfvars file and NOT in environemnt variables.