Oysters with Ginger and Lime

Name: Oysters with Ginger and Lime
Ingredients: finely grated zest and juice of 2 limes; 2 teaspoons caster (superfine) sugar; 1 spring onion (scallion), very thinly sliced; 1 tablespoon chopped coriander (cilantro); 1 small chilli, thinly sliced (optional); ½ teaspoon finely grated ginger; 2 teaspoons Thai fish sauce