func newConfig(opts []Option) *config {
	c := &config{
		Propagators:    otel.GetTextMapPropagator(),
		TracerProvider: otel.GetTracerProvider(),
	}
	for _, o := range opts {
		o.apply(c)
	}
	return c
}
newConfig returns a config configured with all the passed Options.
package otelmacaron
import (
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/trace"
)
type config struct {
	TracerProvider trace.TracerProvider
	Propagators    propagation.TextMapPropagator
}
type Option interface {
	apply(*config)
}